[bodywerks]

I can force a control surface back to center with Hitec 5955's but don't have problems in the air. I would look at your geometry, which should be 1:1 or better(meaning the servo arm needs to be the same size or shorter than the control arm), or you have unequal throw in your elevator halves, or you are trying to pull too tight of a loop, or you are too heavy and your plane is going to be snappy.
Or, if you really do have a problem with weak servos you should have the same problem with the other control surfaces. If it is only the elevators, you probably have a bad servo extension. If they are bargain brand extensions this is highly possible. Anything less than JR or Futaba brand leads are bargain brand, IMO - I've had bad leads from Cirrus and Expert, and bad connectors from Cemark and MPI.