You don't shift your weight forward, keep it back or centered, just kinda push the bars forward a little to counter your upward jump with the rear of the bike. I can do it just about as high with both wheels at a time as I can with the front wheel up method (which is more practical for almost everything). And if your investing maybe, check out a 26 in dirt jumper, bmx bike for big kids! There awesome!
Chuck I think your scale is a little low though, not to be negative or condescending in any way, but I think 6-8 in of vert on a bunny hop is not pretty good. I think pretty good is at least a foot if not more.
Every time I tried bunnyhopping with clips the back of the bike whipped out a little on me and I didn't like that feeling, not sure why?