jobo
Grandmaster
Finally got through this whole thread.
I was just gonna say, "no", upper body strength has nothing to do with punching power.
As a proof, lay on your back and try punching a target above you, then get on your knees and punch a target on the ground, and you'll immediately see the big difference in punching power you have.
thats coz you can get your elbows back far enough or at all