The Cavalier was a developed version of the French Gardan GY-20 Minicab, with revised cabin design, swept fin/rudder and tricycle gear. It was marketed in plan and kit form by K+S Aircraft of Canada (Kay and Stan McLeod), and also by another Canadian company called Squairecraft, but I can't recall off the top of my head which came first. The original SA.102 suffered lateral stability problems, apparently solved by the Cessna 310-style upswept tip tanks on the '.5'. A substantial number were registered as PFA projects, but few seem to have been completed. PFA Engineering should have plenty of data on file.