That plane was designed when multi channel radios were rare, so flying one back then was pioneering. If the plane falls off the wrong direction when the rudder is applied, the wing does not have enough dihedral built in because the rudder does not have enough force to yaw the plane with the flatter wing. If it pulls to the canopy or belly, the stab is too low or too high in relation to the wing. There is nothing wrong with your plane; I am building one, but a lot has been found out in the 40 years after it has been designed that make planes easer to fly. I think your plane looks great and I would be proud to own it. It is not as precise a pattern plane as we know today.