That's pretty amazing! a few thoughts though, he looks pretty good snowboarding and using the opposite arm to balance. But when he's on his skateboard using both wrists to balance, I don't think thats a good idea. Simple runs are fine but when he attempts skateboard tricks, he might easily break his wrists doing it. Fractures of the radial head is fairly common in the position he's in. I can only imagine how bad his carpal tunnel will be also after a while of skateboarding.