I have to respond to this one. My old instructor was 140+/- lbs and 5 foot nothing. I got a chance to watch him work a 150 lbs bag once with 3" punches. I was in awe. At that time he could move that bag more than most could with kicks. I was incredibly fast and I was the one he normally would demonstrated a on in class. I can tell you even when he would just tap me with his hand it felt like i got bumped with 300+ lbs. Somethigng you have to feel in order to believe. He could develope an imense amount of power. I personaly never had a problem with bigger guys. Usually to cocky and never expect to get messed up. That imo is the big dudes biggest downfall. They never see ya coming. I am talking street. In the ring I never had a problem becasue of my speed. Not to say that a big dude can't be fast. I just never really saw it. Also though I never knew to many real muscle heads in the sport. I hope that helped I have to go...................work calls...........