(Maybe the small bass and BG in a typical pond rapidly clean out the small forage, and the large LMB don't have much choice BUT to eat large meals?)
Mostly, I think they eat what is available to them in a range of sizes that are typically between 10% and 25% the length of the LMB. So it kind of works like this ... predation of uniform prey sizes within this limit are function of the number of encounters. It is simple to understand that a 4 lb LMB can have no more encounters than 6" 2 oz LMB (Both of which can and will consume a 2" to 3". They both get the same amount of energy from it and I don't know of any evidence supporting that an encounter with a given prey size requires more energy from a 4lb LMB than it does a 2 oz one. Indeed, I think it more likely the difference, if any, may be ignored. So what makes the 4 lb LMB different? It has to have a lot more encounters than 2 oz LMB for its maintenance. But its just one fish and it's encounters will be limited to the number a 2 oz LMB can have. The only way 4 lb LMB can be maintained by 3" FHM is if it has sufficient encounters. Smaller prey may well limit the ultimate size of LMB. In other words it may only be 3 or 4 lbs but I do think this is achievable.
In a pond with BG as forage, the largest part of the standing population of BG is highly selected by natural selection to evade predators. Even though they can become meals when they get sick, they are relatively immune to predators. Their offspring share the burden of supporting the food chain and the parents have earned the right to live out their lives (which by the standards of swim up fry is a mighty long time). The same problem exist with BG forage as the uniform forage, the smaller LMB get as many encounters as do the big LMB, but if they thin out the YOY to the extent that there is not enough encounters for the big LMB to grow ... then the big LMB has reached the end of its growth.
Let's consider some things we know:
1. When LMB reproduce, they extirpate most minnow types. There is really no refuge, even in two inches of water, for a minnow against a 2" LMB. That's the refuge for 2" LMB ... it belongs to them and in that habitat they are apex predator despite their size. Brush provides little safety for minnows against 2" LMB. Again its a habitat that is refuge for little LMB and they are as adept at negotiating it as minnows are.
2. We know that small uniform prey can support fish and other life much larger than the prey. At one end of the spectrum, BG are mostly supported by insects like chironomids, advancing to the middle of the spectrum trout are mostly supported by insects and crustaceans, and at the upper limit blue whales are supported by krill. Its more about the quantity of food they ingest and their adaptions. I think it reasonable to argue that LMB may not benefit as much as trout, but if this is so I think it is less about trout being lazy and more about the maintenance due to temperature and stuff like that. I've spent a lot time fishing for trout and they never stop moving as far as I can tell. They either have to maintain a position moving water or are cruising in still waters foraging. Can't say they never rest but trout are as active as LMB IMHO.
3. We know that LMB attain similar standing weights whether they exist alone or in combination with BG. BG however, do allow LMB to get larger. Competition between BG and small LMB limit recruitment of LMB and slow the growth of YOY keeping them vulnerable longer to larger LMB. The effect is to provide a similar quantity of prey to a smaller number of fish. We also know that in most unmanaged (for population by harvest) waters that LMB don't get larger than 16". We also know that even under population management growing them to > 20" is less common than <20". So the point I am making here is that even though BG may have the potential to grow LMB larger than minnows ... The possibility of that ultimate weight is more often not achieved than it is.
4. We know the largest standing weights of LMB are achieved with minnows an not BG. To be sure, these experiments demonstrated that the prey couldn't withstand a reproducing population of LMB but all the same the standing weights achieved dwarf what is generally achieved with BG. So the question isn't whether minnows can support a predator fishery its a matter of under what conditions. LMB may not be the best choice but any predator depending on minnows for food needs to be put and take.
5. We know minnows are fairly easy for predators to capture, especially relative to BG. We also know that different organisms have different energy content per wet weight and that the conversion differs depending on the prey consumed. Esox are among the worst (having lower) for energy content and are only modestly bettered by Centrarchid fish. At the upper extreme are salmon which can be more than 2 times as energy dense as BG. Between these extremes are cyprinids which make better prey due to energy density and due to lacking the spiny fins. I don't think I could swallow the argument that a 4 lb bass converts worse on FHM than on larger sizes BG when the same wet weights are consumed. But specifically we should not be talking conversion at all. Conversion only happens once the metabolic requirement is met so the Gross FCR is always high for large fish. The question is how much wet weight of FHM forage is required to maintain a given wet weight of LMB (same for the BG). Only when we understand the maintenance can the true conversion be understood.
Let's consider what we don't know.
1. We don't know how large LMB can grow on FHM or GAMs or RSH. It's probably limited and imagining fish >20" is probably not realistic. All the same we know they easily grow to 13" on minnow If 20" is the limit, then it is some where in between. But to understand how a put and take system may work for LMB, or any other predator for that matter, we have do it first.
If we examine what we know, we have a sense that there is a balance that can be achieved and maintained by ladder stocking and harvest. We have enough knowledge to make a good first guess, and because we have only one predator in a tightly controlled experiment, we can quantify to what extent the guess is off and make appropriate adjustments learning what is appropriate for that given scenario. To be successful, the predators cannot reproduce, the number predators must be limited to such a degree that parental minnow populations can fill the carrying capacity with offspring each year, and finally the regimen must also include ladder stocking and harvest. If the guess is conservative then the predator will outperform while the opposite will occur if the guess over reaches. An optimum system can be perpetuated by maintaining the system and it should improve as nutrients accumulate and as the food web diversifies (eg crayfish, large insects, frogs, etc.)
Or, is the nutritional value of the commercial fish foods such a better deal to feed a BG/LMB pond, that you should just optimize that option and not waste the effort managing forage?
You didn't ask me this question but I will share my thoughts. There isn't any way a natural system can produce the gains achievable with feed. Think about growing 17000 lbs/acre of catfish in 6 months in a PAS system. Of course water quality is a major issue that has to be tightly controlled under such a circumstance. This is for the production of fish. They have to all be harvested at the end of the grow out. For a recreational pond, doesn't it make sense to have water that is fertile enough to carry an above average standing weight of fish but not so fertile to pose risks to the health of fish? I would encourage you to approach your new water from this perspective if you want easier to manage water for recreation. On the other hand, I would also encourage you to grow large weights of fish for personal consumption and other purposes with intensive techniques if you are of mind to do that. What I would encourage is that you might distinguish between them and manage some water for recreation and some water for production.
The reason is that intensive systems produce a lot of waste. Over time this will impact your recreational pond(s) in an adverse way. So I like the idea of producing forage, particularly forage that can grow and reproduce once transferred to your recreational pond. Infusions like this have a lot of potential because the hard part is getting enough YOY past the 1" to 2" mark. I say ... produce these fish intensively but with the idea that forage production pond is full of waste. So I much prefer a forage pond that does not flow into a recreational pond and when I get around to it mine will be below the rec pond and I will fill them filtered water by gravity feed from the rec pond. I will recognize these ponds are full of waste and instead of adding the manure to the rec pond I will grow hay, or veggies, or something else with it as enriched irrigation water. Think about how inefficient conversion is. You feed 10 lbs wet weight feed to get 1 lb wet weight gain. Only 10% of the molecular weight of the feed stays with the fish. That's all. By not letting the intensive water flow into your rec pond ... you are only putting 1/10th of the nutrients into your rec pond helping to hold back the eutrophication of your recreational water.
