dude, look at all the pictures, look at all the other topics about this... they all are about 5 ft and have about a 3-6 ft tranny, and no one's had any issues, if you do just trouble shoot
You'll be fine on speed as long is the tranny is smooth, I'd go with a 4 or 5 foot flatt then begin transitioning into lip. You want a little flat to get your skis set if you're going to spin on