RE: Internal setup for AMA 424 racer
mount the tank as close to the CG as possible. a little forward is ok.
for the throttle, the servo will probably have to be behind the cg. for balance. a standard 2-56 pushrod is what i use. clevis at the engine end and z-bend at the servo. drill a hole straight through firewall and mount. make hole in mount 1/4" so clevis can slide through for engine change.
mount the switch internally, attach a string, with one end out one side and the other out the other side.