On3p sizing

As a starting point, at your weight, most folks would say that 178 blends are way short for you since they're so soft.

181 magnus will feel more supportive for sure, despite the rocker but it's probably a net zero.

Just ride the shit out of them. It's a different enough ski that you'll have a blast.

Which topsheet did you get?

According to ON3P's size guide you should be on 186-191 lengths for freestyle.

My 2cents: 181 seems a bit on the short size for a one of your stature, even if the ON3Ps will probably be a bit more supportive flex pattern wise than said Blends. I would imagine that 181s will have a definitive speed limit (though, said Blends are hardly chargers either). I found 176 Kartel98s to ski too short at my 175cm height, though I intentionally bought them one size shorter than I usually would to try to learn to be a bit more jibby (old dog new tricks gambit failed miserably) ;)

Advice: I would give ON3P a call / email / chat an ask them directly - their advice is usually spot on.