In 1999-2000 or thereabouts, Slimane designed there and the items were cut SMALL and very much like his early Dior collections (i.e. black and white, slim, somewhat androgynous, etc.)
Most of the Rive Gauche items from then were made in France and the quality was very nice with prices to match (I had a pair of black silk pants from one of these collections that looked like something from the 23rd century and the retail was like $650 or something absurd. Luckily, I found it on sale but then realized I'd never in a million years find an occassion ((Star Trek convention or Vogue Fashion Party aside)) when I could wear them.)
Gucci bought YSL in 2001 and installed Tom Ford to design (Slimane, of course, went to Dior). Production moved to Gucci's Italian facilities; suits to Zegna (who also makes Gucci suits). I've only seen canvassed ones, but the earlier poster reported seeing fused ones also. I assume, like Gucci, there are probably a few "levels" of suit. But, the Tom Ford cuts were fairly slim, but were cut more 70's like and sexy... sort of like his Gucci suits but with a slight French twist.
Pilati started after Tom Ford left in 2004. He's doing a really great job, I think. Production is still in Gucci's facilities (after all, they're still owned by Gucci) and the cut is fairly similar to Tom Ford's. It's fairly slim, but I don't think you would need to "size up" in order to fit it, like you would with Dior or Balenciaga. If you are a 38R in general (48EU), then buy the 48 YSL.
Also, RJman, I've seen the Cardin store you mentioned earlier in your great post! I had the SAME impression as you when I saw it...