This is the RCM Advanced Trainer, also known as the RCM Trainer or the RCM Trainer 60, designed by Joe Bridi and included in the RCM Flight Training Course in the early 1970s. Wingspan is 58.5 inches. It has a thick symmetrical airfoil and is essentially a high wing Kaos with a constant chord wing.
Scott Wallace sent me a couple of photos of his RCM Trainer, built from my short kit. This is a beautifully built model. Thanks, Scott!