That's a well done site, nicely designed and informative. I learned a few things about the aircraft I had not known before.
One minor observation, you said the boundary layer inlet panel was possibly made of copper. Having visited WMOF when they were in Hawthorne, I crawled all about the '23 - they didn't even have a rope around her, and I took full advantage. ;D
The inlet panel was plastic, and it is discolored, making it resemble copper. My guess would be some sort of hard urethane, as used in skateboard wheels.