I have the servos installed in my Spark Evo, and Andreas is correct. Much easier to install the servo as you have the access panel there to install the servo. Once the servo is installed you then cut the cover to allow the servo arm to come outside. I ran a Du-bro HD arm that measures 1" to get all the throw thats needed. For servo extensions you will want to run a 9" Extension to get the servo lead out of the wing.

Andrew