Hrm.... HS-101 is good for 28 oz-in of torque.. I would say that is borderline. Since it is a sailplane you will probably be OK. Just make real sure the movement is smooth and free with no binding.
If you want to be sure, any standard size servo will work The Futaba S3003 and Hitec HS-311 would be the best value . If you like using minis, I would suggest the Hitec HS-81, good price and 36 oz-in of torque.