RE: what size battery pack
Also, you asked about how much force those servos will apply to the different surfaces. That depends on the length of the servo arm to where your connection point is. The servos are measured in Oz-in, which means if the length of the arm to the connection point from the center is 1 inch, then you will get 70 ounces at the connection. If it is 0.5 inches, you will get 140 ounces, if it is 2 inches, you will get 35 ounces. Remember that is only at the cable, or the pushrod, when you couple that to the arm on the surface itself, then the length of that arm will determine how much torque you will place on the surface. You now take the length of that horn and multiply it by the force to find out how much torque on the surface.
Curtis