I would trust that the kit CG is correct. Many thousands of Sr. Falcons and Falcon 56 were kitted, and when built true to the plans, all flew well. The Falcon series was introduced in 1964, long before the advent of mufflers and heavier engines. Even the size of engines were smaller then, with the original kits specifying a .35 to .45 engine, so achieving the balance would have been easier, especially with the heavier servos of the period.

Many people thought that the Falcon design was strongly influenced by Doug Spreng's Flattop Stormer that won the Nationals in 1961. The Flattop was a simplified version of his earlier Stormer that he won the Nats with in 1960. Doug's biggest contribution to the hobby was his invention of the digital proportional servo with the 1 to 2 mS control pulse scheme that has lasted to today, 50 years later.