Keep an eye on the thread over at BikeJournal. So far, this is the only response but I'm sure there will be others.

I rode the full 100 several years ago. The area is very isolated and quite interesting. The entire route is indeed rideable on 23 tires. The gravel sections are very short and easily navigated. There is one section of paved rode that is maybe 2 miles long, that is VERY ROUGH. Lots of pot holes and cracks. I recall thinking it was like riding through an obsticle course. Having said that, I'd ride it again if it didn't conflict with the DV double.

We'll probably shoot for the metric at both the Unknown and the Rice Valley. It would be nice to do a full century but I've ridden very little in the last month.