The JR 9100 servos are great servos, but a bit large for most electric TC's. Get a Futaba S9551. If you want a JR for a TC, then get a DS9411.

Size matters when trying to fit a servo into a TC. Most are cramped and the smaller "mid size" servos I have listed above will fit much easier.

If you ever move to Nitro stuff, the 9100 series are awesome.