Back to the original question...
Taking warbirds, the principles and logic of the rebuilds are very simple - hell, even I could sketch out a Spitfire wing construction, and I'm just a journo; but the right materials, certified and rebuilt in the correct jigs... That's alongside Genghis' remarks on the other hand!
The most telling remark is the old saw about 'when the weight of paper = the weight of the a/c you can fly it'...
For a more detailled answser, most of the vintage aviation magazines carry rebuild stories regularly. I can't provide a comparitave choice of these as it's
here. Happy to discuss by PM though.
Otherwise, Williamp, just have a chat with one of the chaps in hangar 2 at Duxford, or any other organisatiion - they'll be happy to discuss (as a rule) provided you take the open approach you have here. "Why are you so slow?" doen't go down so well...
Cheers!