When I cheese it in a race, I put my hands on the tops, close to the stem, tuck my forearms down at a 45º angle with my elbows well below my bars and sit on the rivet of the saddle. It gives me an aero profile and still alows me to put a lot of power down.
Other racers have noted that the position looks like I'm descending. I have no clue how I can even breathe in that position, let alone ramp my speed up to the high 30's.