I have used the Voltz wing maxx servos in a few turbine jets. It will do quite well in the Avonds f-15. The small JR servo I believe is the 3321, its a good one too. The Airtronics 94141 would be a good choice if they fit in the stab. The F-15 rudders are not very big and the jet maybe hits 140-150 so any good metal gear servo you can fit in there will do fine, the linkage is the important part. If you are spooked then just make the stabs smaller to keep the AMA happy. I have rudders on my jet now and still don`t use them but the AMA is happy.

Vin...