Not much help, but I pass a guy on my way to work this morning riding a Bontrager OR MTB frame that was converted for cross duty with 700C wheels and drop bars. He had an aluminum arch on the front fork and rear stay that bolted to the cantilever post bosses, and looped over the tire (imagine a suspension fork arch bolted to your frame). Another pair of canti pivots were mounted to the arch, higher up to accomodade the larger 700 C rim. These arches looked like a commercial product-although it would be easy to make some too-just get some 1/4" aluminum plate and cut them out. I didn't get a chance to ask him where he got them. If I see him again I'll stop him and ask.