In looking at the servo tray and push rod setups, I think you could cut a new opening for an additional servo, elevate it some, and use this as your pull-pull setup for tailwheel control. If you don't like this, then the only other option is to leave the servos as designed, the rudder one becomes strictly tailwheel, and look at placing the rudder's servo on the aft of the fuse like you see done on 3D planes.