My only experience with wide tire/narrow rim was not good, and it was with some cross tubulars. Last fall I hoped to get better winter performance, so I put some Vittoria 32 mm diamond-tread tubulars on standard tubular rims. The tire stayed on, seemed to be well-supported, and generally didn't do anything wrong. What I lost was the ability to remove/install my wheels without deflating the tire and pumping it back up! The brake had to be adjusted so it would grip the brake tracks well. The brake QR is designed to open up to release up to 28s (it seems). When I thought I would get some wider tires for my tour this summer, I decided on CR18 rims rather than Open Sport, Open Pro, or Aeroheads, just to address this issue. The wider brake track requires the brakes to be set wider, so when the QR opens, the inflated tire should be able to fit between them. At least I hope so!

My wide clincher wheels should be ready any day, so maybe in a week I can provide some on the road feedback. I'll be getting Pasela TGs for them.