Replying to Surface Blanks

Okay so I have decided I am going to buy surface blanks. But, before I click the buy button I just want to know if I should get the 170's or the 180's. I am advanced park skier and ski very aggressively. I am 16 years old and 5'8, so if I'm gonna dump $290 in to this I want something that's gonna last. I'm still growing and don't want to buy something I'm gonna ski for a year and then have them not fit me anymore. Also, if anyone else has surface blanks how do you like them?