Having raised rainbow up to 16 pounds all that is required is feed, a really large rearing pond with good flows and floating feed. You take a normal WDFW lake plant Rainbow and raise it for two more years you can get them rather large. One year will get you between 4 and 8 pound fish. Jack Marshal up near Centralia grew Donaldson Rainbows for market and taught me how to do it. The trips? Nah they did not perform as well in the growth for some reason.