Start em off early and anything is posible. I knew an 11 year old who could bust a 360 flip down an 8 set no problem. I guess you dont car about fucking up so much when you are young.
i was kinda similar when i was young, used to jump off high walls and everything.
when i used to play football at school i would dive like a premiership goalkeeper on concrete, i still do sometimes but it hurts every now n then....back then it didnt hurt atall i used to just bounce off of things.
but yes i didnt break a bone in my body till i was about 14/15 i think and that was only my nose, wernt even a clean break