It's all about population density. The less bass there are the bigger they will get, there will be more bluegill and thus more food per bass = bigger. Lots of bass eat young bluegill allowing the larger ones to get more food that would otherwise be eaten by the more numerous smaller gills = larger bluegill.
If you want larger bass and don't mind your bluegill being stunted go ahead and put minnows in there, the bass will leave the bluegill alone but their size will diminish over time. A stunted bluegill population can be very difficult to recover from however. The bass will get larger, yes. If you want large bluegill, then stock some more bass to lower their numbers. Bass won't get huge though but you might get some really hog sized bluegills. Sounds to me like your balance is pretty good with small to good sized bass and I'm assuming harvestable bluegill since you said hybrids. If you just want bigger fish in general buy a feeder with a timer. Your place in Crittenden by any chance?