Yes, you can. A push-pull installation using two rudder servos in the tail is the absolute best to equalize forces on the rudder post and hinges but I've used many single servo tail mounted installations and never had an issue or failure. If you don't need the weight or torque of a second servo in the tail a single servo installation works just fine. My 35% Giles still uses a single tail mounted rudder servo and it's doing just fine. I make it a point to use 10-32 hardware for the rudder horns instead of 8-32 for a safety factor. I've managed to bend, in flight, every 8-32 rudder horn screw I ever used.