I also had an issue with tail flutter. There is another post on this...I came to find out that the carbon spar needs glued to the bearings. That has removed the slop from the spar, however mine still has a bit of flutter. Servo is a Hitec 645, which has plenty of holding power.

After doing some research on the matter, I come to find out that balancing the elevator should solve the problem. I added 1 once of lead to each half to test the idea, however my engine did not want to cooperate...so maybe Wed.

Hammbone...what motor and prop are you using?
Thanks,
Eric