I used to do those underhand grip presses and they hit your triceps. I never found they hit my delts or chest at all. I did them for awhile and you can go quite heavy but I used to aggravate my wrists that way somehow, so just switched back to CG bench press, which I find a better exercise anyway. As for what mudge said, I think the way your chest develops is like everything in the body, genetically predetermined. Although the chest is always referred to in sections, I believe it grows how it wants. As for incline presses, these feel so much better for me than flat,and although I don't go as heavy with these as flat, im sure I got more growth from these than flat etc. Having said that Incline dumbell press does nothing for me, whether I go heavy or just do higher reps, it always feels in my shoulder joints. Now Flat dumbell press hits my chest better than benchpressing. I just don't get it.