Interesting build Phil, takes me back to the early days of control line flying when you could get kits for "whip" control models, the construction was similar to your Mustang. I had a Typhoon for whip control, it "flew" on a length of button thread tied to a thin garden cane. The Tiffy was flown in the road, the only thing limiting the line length was the proximity of front garden walls, apart from grinding off the bottom of the model on the road, it was a lot of fun. My final whip controlled model was based on a KK F9-F designed for Jetex power, slightly different from the Typhoon, the F9-F was controlled with two lengths of button thread and a conventional bellcrank and pushrod for a tiny trim tab/elevator on one half of the tail plane. Same type of construction, just sanded and doped profiles and a few lines drawn on with the (then) newly invented ballpen called "Biro", to represent control surfaces etc. Couldn't do it now, thinking about it makes me feel dizzy.