Where you mount them has way more to do than the length when spinning. An even swing weight is what matters. Don't mean to claim here, but I used to ride 155s a couple years back mounted at 6cm back and could only spin at most a really ugly 5 on them no matter how hard I tried. The following year, I got 170cm S3s mounted at near center and within a few days skiing the park, I was able to throw tens fluidly. The ski length did not affect me much, but the mounting position did. For reference, I'm 5'7" 130lbs.