As the others have said, your pond goals really make a difference. But, with that said, I regularly cull 6-inch bluegill. Because I have a regular feeding program, my 6-inch BG are plump. On Saturday I took out nine 6-7 inch BG and one 11 inch crappie. They get filleted, skinned, and each fillet gets cut into three pieces. So, Saturday's fish provided 60 pieces that will get beer-battered and fried. With just a couple more, we'll have enough for to feed a gathering of eight people this weekend.
I regularly catch 10-11 inch bluegill, but they stay in the pond as breeders.