What's an A/B/C model? I'm not familiar with those.
As far as design changes go I plan to modernize the construction with alignment tabs and a large front hatch to allow for quick battery changes and access to the radio gear. I'm still on the fence with the wing... don't know if I'll design it as a built-up wing or stick with foam wings. I might be off my schedule a bit as I just took on a project for a fellow club member; I'm building a 50cc sport plane for him, but I will get something 1/2A size in the air this year.
-Jaime