Controline stunt planes have been modified into RR planes for years. I have a Veco Thunderbird with a fourstroke OS 50 in it and it is a great sport flyer. Used the flaps for ailerons and put a live rudder and steerable tailwheel on it and balanced it just as it would have been as a controliner. It flys great and not much faster than it would have as a controline model. Loops can be made fairly tight and the rolls are fairly axial but a long way from pattern quality. Landings are about controline speed.
As far as making the wings equal length it helps but is not an absolute necessity. Build it straight and balance it properly and it will most likely fly well.

Here are some belated pictures of the Thunderbird as described above.