Pro cyclists adopt many different positions so that they can descend as quickly as possible. In this video the guys at GCN have some tips on how you can get aero to descend fast.
Good GCN…. but this is better. http://youtu.be/Svs3RPMGEEA
This is how you descend like a pro with no fear, brass balls without aero tuck! Go Super Mario! Good bit is 5min.40sec onwards and at the start when Mrs Cippo wifey cops a feel on her booty from Mario. Noice.