Interesting question DD1. Is there a lot of variation in the shape/size in the F1's?
Which gets me thinking. Consider what makes GG special - big mouth and aggressiveness which helps them attain maximum BG size more quickly and easily than pure BG. Pure BG can get near 5lbs and it seems like GSF traits (big mouth/aggressiveness) are responsible for the rapid growth in GG. GSF already have the traits that should make it easy to manage them for trophy size (1 1/2lbs). If you can live with a fish that lacks the BG size potential, and be happy with fish upwards of 2lbs, then why not go with the pure genetics of the GSF? That way you don't have to change how you manage for future generations. In fact you can actively select better fish and improve your fishes genetics.
GSF are everything that GG are (just smaller)(and better LMB forage)(and genetically pure).
Which brings up another possible misconception about GSF, that they aren't as fecund as BG. What about this:
"Spawning occurs in Lepomis cyanellus when the water rises above 21 degrees Celsius (70 degrees Fahrenheit). It is thought that L. cyanellus may produce the same number of eggs as Lepomis macrochirus, which is roughly 50,000. It takes normally 1 to 2 days for the eggs to hatch and another 5 to 7 days of protection from the male until they become independent (Parr, 2002)."
It doesn't make sense to say on one hand that GSF don't reproduce enough (to be good forage), and then say that they tend to overpopulate (leading to stunting). Seems that GSF reproduce just as much as other lepomis, but are preferred and preyed upon more by larger predators because of their shape.
The common wisdom about Green Sunfish isn't adding up.
