511, a 171 is maybe a little short. How long have you been skiing, aggressivenes, etc? Im 5'7, and im on 176 t-halls, and i might get 171 invaders, or 175 tnk
Definitely go ~180. If your really against going that long for whatever reason and you feel weights gonna set you back with a 180 go in the 175/176 range, nothing lower though.
Where are you mounting? If center then definitely 180 imo.
Where are you mounting? The only issue you'd have is tails, if you mount center, the 176 is going to feel way too small, even if just a couple + from reccomended, go 180, its just 4cm but it'll go a long way