since hes starting off, a low/mid 170 would be perfect. but as for anyone good, theres no excuse not to be on a longer ski. im 5"10, 165 lbs, and i ride 183s in the park, and i think those are too short. i have No problem buttering onto tech rails, spinning on, spinning in the air (can whip flat ground 3s around like it aint no thng). they just ski soooo much better as you go bigger. just gotta make shure its a light ski. thats all.