3a 3b you say? Then you probably won't need to relax on the sides (although to keep the look you would need to rebuzz with a guard every once in a while). If you get flyaways, smooth them down with a bit of a pomade (my brother is 3b and his is kept around that short on the sides - it's not enough hair to curl into a 3b pattern).
I hear growout is a b*tch, though - be warned.
I considered this haircut, but decided I prefer the versatility of being able to pin it back when I want to, and having it all down when I want to. That cut, while gorgeous, is a little more limited in that way.
But if you really want it - go for it! I still think it's a very sexy cut!