Your bluegills may be on the small side for several reasons. Trying to get their size up with feed in a 20 acre lake sounds like a waste of time to me. Addtionally adding hybrids will not help much.

Here are some possibilities why your bluegill are undersize.

Overharvest of bass in the size range most efficient at keeping bluegills in check, therefore too many bluegills.

Poor recruitment of bass so there are not enough in that size range, and only really large ones that prey on large bluegills. This is related to the following point.

Too much cover for bluegills that keeps their numbers too high.

Too many really large predators like flatheads big channel cats etc. that prey on large bluegills.

To much competiton from channel cats and/or crappies that are competiting with small bass keeping bass numbers too low.

Crappies eating yoy bass.

Competition between Gizzard Shad and bluegill that is detrimental to the bluegill. (Documented in Indiana reservoirs).

Feeding or adding hybrids will not solve your problem. Thinning crappies may help some. Your really should have someone come and electroshock and do a survey to see what is wrong.

If pigs could fly bacon would be harder to come by and there would be a lot of damaged trees.