David I'm certainly not one of the experts here by any means, but I can share a couple of my observations. My LMB and now larger BG wise up fast. We all have stories of catching a fish more that once in either a day or in a period of a couple of days, but my experience with my little pond (1/4 acre) is that I can fish it hard one day, catch and release plenty of LMB, then not be able to buy a fish out of the pond for a week or so. I may have caught all the aggressive bass, I may have caught nearly all the bass, the "word may be out", it's hard to say.
My point is that LMB learn to avoid being caught. They do seem to forget the danger after a period of time. We know there are plenty of fish in the water as we can see them glowering at us. (What's the emoticon for a glowering LMB?)
How many of those cull LMB did you introduce? My guess is they would be the only catchables in your new pond? How much do they have to eat, i.e. are they hungry or well fed with CNBG? Could they all have wised up? I've fished a river for years with what looks like "flocks" of SMB crowding around my fly or lure-40 or more fish staring at the bait. A few will eventually take the fly; the others will try then to grab the fly from the caught fish's mouth. Once that fish is pulled from the water, the others go back to staring at the fly. It gets progressively harder to get the next one to fall for the ruse.
It certainly may make sense to add other genetic stock, given that your bass were culls in the first place. Why were they culled-simply too many in your buddy's pond, poor WR, some other reason?
You will get some expert advice soon. Keep us up to date on the progress of your fishery.