Seems like the original plan to stock only large LMB in a pond full of BG and crappie is a good one. It doesn't matter if the crappie eat all the yoy LMB. The LMB will feast on the BG and crappie that are of a size that suites them, and if super plentiful feed was the only missing ingredient to XL LMB, then the plan should work. If some XL LMB die of old age, so be it. That would also happen in a more traditionally managed pond. The more difficult part, it seems to me, is managing the forage pond in which the stocker LMB will be raised. As long as it produces an adequate supply of proper sized LMB, everything should be a go. If some BG and crappie get too big for the XL LMB to eat, catch a few trophy sized pan fish.