One of my friends lost a Titan to a DS821 on the Aileron. I would not recommend using them on any of the controls. Barracuda is right about the dampeners replace them if you are in doubt and be SURE to lube them good with Dielectric Grease. Be sure to check the grip bearings. A notchy bearing can cause a woof. Be sure to put the thrust bearings in the right order when you reassemble it. I grease my thrust bearings with dielectric grease. If all that doesn't fix the problem try another set of blades to see if it fixes the problem. I saw a set of Thunder Tiger Carbon blades that were bad about woofing. After Hours of trying to fix it he borrowed a set of V-blades and the problem went away. Are you running stock mixing arms? The most I have been able to get out of stock mixing arms is about 22.5 deg. range. I have my Raptor 50 set up with OS hyper 50, MP 2, 8.7 gears, Radix Blades, Kasama Head, Throttle Jockey, HS-6975, 9252's, 401 w/9254. I run it at 1950 rpms, +/- 12.5 deg and don't have any problems with it bogging.
Check out my friends website it has a helpful site with lots of tips for Raptor 50's.
Raptor Technique