I'd be surprised if that was truly 35mm. Most vintage Vacheron Ultra Fines (Ultra Thins) have been I believe closer to 33mm. Maybe the dealer was estimating size upward a bit, as anything under 36 is probably a tough sale these days to most men. Its only been since the release of the VC Historique 1955, around last year that they have been making an Ultra Fine watch that is 36mm.
It's funny, I don't wear watches to black tie weddings but I do to other black tie events. Not sure why I do that, maybe subconsciously I feel rude at a wedding for the reasons you mentioned Dino.
I ordered 2 watches from Ben, one of which I'll try as a black tie watch. And when my wife stops spending money landscaping the backyard I'll be on the hunt for a vintage VC for black tie or dressier occasions. Dino, when that hunt starts, expect a PM haha.
Landscaping sucks...we have to do a little of that this year. I look forward to your PM and sharing some input when your adventure to find a VC begins.