RE: Low wing trainer
After mastering a 40 size primary trainer, I generally recommend a Sig 4 star 40 to my students as an intermediate trainer. You can use the same radio, motor, etc. but with the low wing and the improved aerobatic capability, you can't go wrong. There is just enough extra performance to take you further up the rc learning curve into serious acrobatics. A 3D plane it aint but 3D sillyness is not what you need as an intermediate trainer. The 4 star 40 is available as an ARF or a BIY kit.
good luck
Ray Foley