Can't feel pecs very much?

Yeah you don't really feel it as much on flat bench but it does work. It stretches yr chest out more than making yr chest grow outwards which gives you a wider chest with pecs like slabs of concrete rather than logos ones that stick out far from just using dumbells. If yr chest is feeling really weak at the end of a workout and you can't tense it properly then You know you've done a good session. Try doing flat dumbell bench aswell and all the other ones cos you seem to feel it more on them.