As above the only real place to put an aileron servo is in the motor mount area which isn't so easy. First I mocked up the size like in the photo.
I marked the area around the servo and cut it out SLOWLY keeping the cut as level as possible. The servo mount brackets slide into little cuts to help stop it twisting.
Even after cutting out that area the motor area is still pretty strong however I don't want to risk it. I added 2MM carbon fibre rod across each side just for security.
The wings are thin so I didn't want to use pin hinges, instead I use OHP (Overhead Projector) sheet to make my own hinges. Cut out or press a hole in each side to give the CA something to bite on.
The wings still need to be removable so it's a case of pop of control lines. They are various ways to do this but the quickest and cheapest is to use carbon fiber rod with a single "L" metal piece towards the top. Use heat shrink only a little piece to secure the rod to the carbon fibre and use CA glue to set it. This allows the metal to move, see the photo.
The aileron starts 30MM from the wing when inserted in place. The length of the aileron is 15CM long by 2CM wide, its a good size as I don't expect the servo to push it all that far down given the position and angle.
Now everything is all in place and working and as I thought the servo pulls more than it pushes on the aileron. This is OK though as it will still work as expected, the second benefit is the servo is almost directly over COG so it won't offset the balance so much at all.
To hide the servo I used some sticker sheet I had left from other models, the camera flash shows the outline but otherwise its pretty dark and hidden.