Another option is to mount the servo in the wing cavity and use a pair of rods from the servo to the elevator. I use a pair of Sullivan Carbon rods fitted with the proper hardware on either end. On the servo end, I take one short length (two inches or so), sandwich that inbetween the two long rods, wrap it with cotton thread, then put several drops of thin CA on the cotton. This will solidify the whole thing into one.

Then you put a threaded rod into the short length so that you can attach that to the servo clevis, and on the other end, put the proper sized threaded rods in both ends, one on the right and one on the left then fit that with clevis'.