So, Joe, I was just perusing some of the old posts on the C3 site. Did you ever get the body off? When you say the panels are attached, do you mean they are glassed onto the rest of the body making it one unit bumper-to-bumper? Are the bumpers urethane or fiberglass? If they are urethane, you probably want to separate them from the body. A flex agent is used in the paint on urethane to keep it from cracking.
If you're still working on this and want to discuss, send your phone number.
Sorry it took so long to respond. Good luck.