Original owner of a Big Comanche survivor

@hingeman, my comments are in addition to @Marleysky's regarding the model's debut in early 1960's along with photo and Cox Sportsman .15 (I don't have one). May be @Mark Boesen has one? That aircraft, although wonderful among Cox offerings, apparently did not sell as well as the smaller RTF's and was short lived. Regarding fabricating your own parts, I did that back in high school in the early 1970's.

I purchased from Gemco (forerunner to stores like Target and Walmart) in Waipahu, Oahu, Hawaii a Cox .049 P-51B turtledeck RTF parts plane during their tent sale. I think I paid $2.00 for it then. It was new and complete with postage stamp back engine and 3 bladed prop, but was missing the box, bottom rear half of the fuselage and movable elevator but was otherwise complete with wing.

At home, I fabricated out of 1/16" thick balsa, a new elevator fastened with cloth hinges, halves with music wire, and a new rear bottom fuselage section. It was squared off instead of the scale round corners for simplicity. I used a standard half-A control horn to a new pushrod I bent out of 3/64th music wire to the factory bellcrank. I sealed the wood with sanding sealer, then painted the balsa parts with olive drab paint reasonably close to the mold plastic color.

When done, now I had a functional plane and was pleased with my results.

It's up to you how far you want to go, but I gather you are probably right, it would be nearly impossible to find the factory repair parts for your plane now. A few here have done as you are thinking to do, manufacturing their own parts to have a complete and representative RTF.

Regarding patterns, on Outerzone doing a search on "Comanche", did find two CL models of 36" wingspan that should be closer to what you have.

Outerzone Plan# 9122 - 36in Robbe Piper Comanche CL
Outerzone Plan# 7234 - 36in Aeropiccola Piper Comanche 1958

You could scale the elevator accordingly, and use theirs as a pattern. The telltale sign would be the factory width of the elevator, using that dimension instead of true scaling dimension. It ought to reasonably bring you close to what you are attempting to achieve.

Take your time and imagination, and I think you'll come up with a suitable solution to restoring your Cox Piper Comanche. Good luck, George