Here's my take.. I'm pretty new to this sport too, but like you I grew up racing motocross, bmx, and offroad. So doing freestyle on jet skis sounded like pie to me.. DONT jump straight to an aftermarket hull... Why do you want to spend 10k so bad right now when you don't even know if you'll be able to stand up? Spend 2,3,4k on either a sn or RN SJ.. Learn to ride aggressively, carve, buoys, tail stands, nose stabs, learn to slide the ski..all the basic fundamentals.. I know you stated you've ridden before, but it's an entirely different feel from a motorcycle.. And it's gonna take a lot of adjustment to get used to it! I guarantee you if you buy an after market hull, you won't flip it for at least a year, maybe 2, maybe never! Ive gotten pretty good over this past year and Im starting to ride the ocean more and more and I always tell my self that I can easily roll or maybe even flip... But as soon as I have the wave in front of me.. It really puts you in ur place.. It's not as easy as it looks..
Btw I ride a square nose.. And LOVE it! I will switch over to a RN before I even consider a aftermarket hull.. Just my .02