Your edge/speed combination might not be what it needs to be. Try edging a little harder, with a little bit more speed. You'll have more pop off the wake, so you'll have to slow your rotation down just a little bit. I've found that the more pop/height I get, the more time I have to rotate around, and spot my landing... That alone makes landing the tantrum a lot easier. Be sure that you aren't initating the flip too early. Some people, including myself, get a little anxious and actually throw the backflip before leaving the wake. Also, I've heard grabbing indy helps out a lot. When you grab indy, your body tucks, which makes you rotate faster. Try those few things, and I'm sure you'll be able to land them all day long. Let me know how it works out.