Please CHECK YOUR XCELL power consumption!!!

A single formula will help you check you SERVO POWER Req.

Watts = (torque/speed) *.0074

Then

Amps x Hour = Watts / 4.8v

To get the Mah multiply by 1000.

Do the exercise for all your servos look at the manufacturer specs and you'll be surprise. Specially with the little innocent 27.8 oz of torque servo you have in the tail.

I swap all my Xcell servos for digitals and believe me the DRAW power.

Check for ANY binding as small at it seems.

Saludos,

Good luck