I have had good results with the Hobbico CS 35. It weighs in at 2/3s the weight of a standard, but has better speed and torque. With 6v they have around 72 onzes and 0.11 second in speed. The cost is about $25. Tower has the generic version TS 35 for around $20.

I have some in an OMP Yak for 3D and they hold well.

They have a smaller case. If you are building, fit the openings to the servo. If not, add a bit of plywood to the opening.