For a timber framing tour of Normandy I know several people, and can probably get you in touch with François Calame who was instrumental in the trait bid for UNESCO recognition. And if I can't find anyone else (highly unlikely), I'd be more than willing to show you around. Message me and we can talk possibilities.

I'll take a look for that book. I have a feeling I've seen it referenced somewhere before. Another great reference is Émery's "La Charpente en Bois". If you already have a reasonable grasp of le trait then it makes a fantastic reference when you can't quite remember how to find a certain angle or length. Or just when you want to learn something new.

UNESCO seemed to think that there was some unique characteristic of French trait. I'll try and see if there are more details on the decision that might shed some light.