I used standard Hitec HS425BB servos. I didn't feel comfortable with anything smaller. 20 minutes with a dremel and the openings in the wing were big enough. I attached the servos to 1/8" plywood plates with hardwood blocks. They are not glued in. With a .91 four stroke for power I wanted the extra security of a standard size servo and the modification is a simple one. Let me know if I can provide additional info. It's a fun little airplane and you won't see many like it at your local field.