I ride the drops more than anything and if I want to go downhill fast I do the 'Urs Zimmerman'! If I am on the drops and the road gets a little rough, etc. then I stay in the drops or get onto them and ease back in the saddle. This gets my c.g. back a bit and keeps it low. It's just my technique (and Urs'!) so your mileage may vary. Have fun!
This is an internet screen grab pic