Knowledge is power.. I don't think it's the size of the tiger, but the heart of the tiger. Put two guys against each other, one being 25kgs heavier. What good is his weight going to be if he's unfit or he grabs you ? Bigger people tend to grab a lot and use their weight and strength that way. Bigger people are mainly for strength, not skill. Any person who does martial arts knows someone is a fool for grabbing you, no matter how big they are. Knowledge is power, I have a friend who is about 55kgs and I'm 75kgs. He's been doing martial arts for 10 years or so, I've been doing it for a half a year.. Who's gonna win ? He is, he has much more knowledge. Where I could probably hurt, he could kill with one or two strikes. Hit anyone in the jaw, no matter how big and they're gonna go down. Lennox Lewis got knocked out by a much smaller dude who was unheard of that way.