Jame , as others have said, try to get everything as far forward as you can. A BVM or Hanson type UAT will fit very nearly behind the nose gear wheel opening between the steering cables without modifcation. I also used a Wren SS pipe to keep the rear light and was able to get it to balance with 2 2200lipos in the pockets and a 3700 Ecu batt in the nose. I have a 19lb turbine in mine and couldnt be happier.
You may have other reasons for using JR servos in the back but if its because of the fit, I have 7985's in my stab and they fit great.