the hitec servos have good torque- they have had some complaints about centering if on a surface that has a lot of throw, as on 3d planes etc. but they may be fine for your extra 300.

alternatives are the futaba 9001 at about 55 ozs or the 9304 which is a relatively high torque servo rated at about 70 ozs i believe.

just giving you some choices here.

ed