Another thing, make sure you are cutting all the way through the wake and not flattening off. Sometimes you can't even tell if you are doing this, just others in the boat and notice though. I had this problem for a long time and when I finally got it, I noticed a huge difference. Make sure and keep your wieght balanced over your board (not on your heels, but your body should be balanced over the board and on edge which of course pulls against the boat causing lots of tension), and edge through the wake and stand tall resisting the tension of the line. When you release, the tension and standing tall off the wake will pull you up and into the air.
I've seen a guy throw Raley's, mobes, and tons of crazy ch*t off a ski nautique with no wieght and no pylon. Its all about getting the right tension and progressive cut. Or you can just make it easy on yourself and go out and buy a Byerly board and a Super Air Nautique and throw about 2000 lbs in there and no matter what you do you'll get 5-10 ft of air