The correct descending body position involves standing and staying centered with your weight on the pedals (not getting way back), legs relaxed and bent (not squeezing your seat) and arms bent in a half push-up position. Remember, I didn't invent these skills I have been fortunate enough to learn from the best (World Champions Marla Streb, Greg Minnaar, etc.) and learn from the great riders that I coach (Ross Schnell, Mitch Ropelato, etc.). I am simply passing on what I have learned.
In these videos taken by a student in my Philly mountain bike camp this spring you can really see one huge reason (there are many) why centered is good and getting back is bad.