Anyone who watched Stage 19 of the TdF saw SS bomb the backside of the Golibier in a full tuck position to bridge the gap up to the group of leaders. I, for one, was pretty dam impressed. He pretty much pressed his torso flat against the top tube, butt below the saddle, and hands on the bars close to the stem.
I've tried it a few times but the bike gets nervous as I get above 50mph, which also gets me pretty nervous... I keep my pedals level and press my thighs against the top tube and knees against the forward part of the down tube. Am I not applying enough forward pressure to the bars?