Ambush,
Something that helps me is to SIT UPRIGHT when doing the wheelys.
1) the front comes up easier
2) I can feel the balance point/height of wheely easier.
As a matter of fact, I sit back (perhaps only 1") further than normal.
So:
1) Get rolling at 5k in 1st, hold steady.
(If you're getting 6 inch high wheelys, move the RPM up to 6k... that's guaranteed 4 footers.)
2) Sit back a tiny bit, and sit upright.
Be sure you're going straight, on a straight piece of asphalt. (Not seriously dipping.)
2.5) Cover rear brake with foot.
3) Whack the throttle full on, and hold.
When she comes up, all your mental energy will be on determining how high is it, how fast is it coming up, and throttle management. Work on it... you'll get there!