Not surprisingly, hybrid's growth potential generally falls somewhere in between the growth potential of the parent species. When one studies the state records throughout the U.S., most bluegill X green sunfish records are smaller than the pure strain bluegill record. In the states where the hybrid record is larger, there is the possibility that the fish were misidentified or possibly redear/bluegill cross. There's the "great myth" of the bluegill/green sunfish hybrid being some spectacular growing fish with great top end growth...in reality the BG/GS hybrids probably just have a nice early growth spike due to the larger mouth and ability to utilize larger forage early in life.
Anyway, in answer to the question, I'm making a semi-educated guess that you would have the best top-end growth potential with the following crosses in descending order.
BG X RES
RES X GS
BG X GS
This guess is based on some personal experience and by averaging the growth potential of parent species. I'm willing to take a beating from anyone who disagrees with me.
