RE: Control line trainer
Fortunately, when it comes to trainers, almost anything will fly. Since you are not stressing optimal performance, any...or no...airfoil will work.
A fuselage with reasonable moments, C/G, and a sufficient stab/elevator will make it go up and down.
Sturdy (but not too heavy) and easy to repair are pluses. TLAR really does work for a trainer.
George