I have collected a couple older trainers and I can't track down the original plans. Once you have done modifications to a plane, what's the general rule about a balance point, front to back? The thickest part of the wing, and then trim it out and see how it flies? I bought one and there was much lead epoxied to the firewall and wondered once I added some tail weight in terms of new hardware and larger tail fins, and just wondering how to predict balance, when the plane is modified, or original plans are not available.