When I did my 540 28%, I placed the throttle and choke servos
in the cutout just forard of the wingtube. Used a dremel to enlarge
the small hole in the firewall, so that two carbon fiber rods could be
used for the throttle and choke control. The favored West Coast
version. It keeps the servo to reciever wires on the right side of
fuselage, away from the ignition wiring on the left side. Music wire
without some kind of metaless connector at the motor would be a
no,no. Almost certain to cause RF noise. Not all recievers have
RF filters or chokes built in and you could have trouble. Be very
sure to do a power on range check, no matter how you do it.

Gerald

Cutout fwd of the wingtube, right side of fuselage.