I a dive the airplane will actually go over the pitch speed of the prop and wind up the engine even faster than it runs in level flight. At that point the prop is acting like an airbrake. Whether or not it's 10% over is up to the model design, weight, prop diameter and probably what you have for lunch but 10% doesn't sound too far off. Just to err on the side of being pessimistic call it 120 mph and calculate the servo load based on that then mulitply by 1.5 and go shopping for servos with at least that much torque.

As I suggested you do NOT want to be too close to the stallling point. THe power demand on the airborne battery is far higher than a stronger servo that is well within it's limits. And the stronger servo also means you'll retain the transit speed instead of a struggling longer time so the controls will react more consistently.