Step ups are for getting into big (8-15ft) waves earlier and going fast down the line. I recommend something about 6" taller than you.

This model is designed to paddle fast, take off on critical drops, bottom turn, and then hit the gas down the line! It has curves as well to be able to rip carves too.

The board is stretched a little thicker than a shortboard so it can paddle much faster. I thin out the nose and add rocker so that it can make drops and turn easily, which is critical in larger surf. The middle is relatively wide for this style of board. I like it because it gives extra paddling volume for easier take offs and planning area to go faster down the line. The tail is thin and narrow, which provides supreme stability when you're on rail. And I kept a little extra tail rocker so that you can still make performance carves and airs.