On some really steep downhills, my belly does really hover right above the seat. I have been told that I keep my weight a bit too far back, but that's what I'm comfortable with now.

I do have to open my knees a bit to get my thighs around the seat, but I don't keep them that way once I"m past it. It does feel silly - I think I look like a punk kid riding a BMX bike - but when you get that bike/body separation, it makes a big difference in how much control you have going downhill.

What kind of saddle are you using? A narrower saddle really helps with this.

I have given myself some really nice bruises wiping out on downhills, from my thighs hitting the tire:
http://w3.gorge.net/gab/bike_ouch.html
(top & bottom photos)
(Note to the squeamish: if you can't handle bruises, don't click the link.) It looks bad, but trust me, it's still better than an endo.

gabrielle