I found a great new servo from futaba that I am using on my Trex. The S3110 here are the specs.

S3110 Micro Servo-J
FUTM0046
Volts Torque Speed
4.8V 22.208 oz-in. 0.1 sec/60° (deg)
6.0V n/a n/a

Dimensions Weight
0.9 x 0.4 x 0.8 in. 0.26 oz.

I use it for all 4 servos, I found it to be a great analog tail servo with my GY-401 gyro. Also I should mention that this is a very tight servo, in that it has NO noticeable slop or centering issues.