The whole of the pectoral muscle structure (major-lower, minor-upper) are worked together when doing declines.The main focus and work load is put upon the lower (major) portion. The upper pecs (minor) are receiving much less effort. Same thing with the flat BP, the lowers take over the main movement or function. The decline press is indeed underrated , but really not needed by most men. Unless they have a need for thick lower boobs. To hit the lower, inner and portions of the upper pec's the wide gripped dip may be preferred, in most cases..
How bad would that side chest shot of Arnold be if his upper (shelf) pec were flatter and less developed? The reason that the upper pecs dominate when considering a superior looking total chest.
Body-M: Might try tbe BP to the neck (Gironda style) with a wide grip, elbows back. But have a training partner (or safe stop's, etc) stand by. Not designed for heavy work, moderate weight suggested as this is a pure BB'ing movement. Go easy and light at first. Can also be done with DB's, with attention to keeping them inline with the throat/neck, elbows wide out. Can do these on a incline bench. Though too high an angle can shift the work load to front delts more than the pec's. Pec Deck (with elbow pads, not grips held out), with the elbows kept high and inline with the head. Cable crossovers. bend at the elbows a bit. Crossover high to head position. The flat/inclines or knelling version. Front presses, or most any other overhead pressing, will hit the upper pecs also, but to a lesser degree. Good Luck.
