Push yourself on the cardio and abs. Do a couple of P90Xs for reference/ideas

One thing that I added last year and have noticed a big difference was;
Find an adjustable cable pull machine, place the pivot pulley up about head height, use some kind of T-handle and do standing chest pulls.

Stand like you stand on your board, I do sets of thirty to get the stamina up, hold your core and bend your knees slightly while doing them. I do these as part of my standing upper body routine (curls, tris etc) and each time through I switch which leg I put up front.

Hope this makes sense. Basically I try to mimic my wakeboard stance as much as possible. This has helped a lot for me and I am OLD!