having trouble?

ive heard alot about bigger bait for bigger fish. so i went out to get some bait blue gill. ive been using creek chubs 2"-5" for a couple years and my biggest cat is a 35" flat head on about a 2.5" chub. so in trying to catch bait blue gill i ended up with a few 4"ish long ear sun fish, which ive never caught in the rivers, but i figured theyre close enough, since ive never caught creek chubs in the river. tried them a couple times with no success, i only have about 5 hours fishing with a sun fish in the water, but not a single bite. im just wondering if its location, bait, luck, or just lack of patience. i really want to get into some large flat heads. do i need to get; right up against a dam, blue gills, or about 25 more hours of waiting to get one? any advise, as vague as it may be is greatly appreciated.

well, what are the most common prey fish in the river? i usually fish the allegheney a few locks up from the point. shad, blue gill, baby small mouth or sauger, suckers, creek chubs? ive caught them all once or twice except chubs in the river.i very rarely catch species other than bass cats and carp when fishing the rivers. and wouldnt know how to target them in a river. i have a boat but its hard for me to get it out on the weekdays due to my work schedule. just need a little guidance to get to the bigguns. thanks all