I've mentioned on this forum before that I was intrigued by the C17, more from the angle of not having to worry about rain at all.
It's a little OT, but in the light of this and @
jonc123 's comment above, maybe I should say that I've never had a problem with the B17 and rain. I have mudguards/fenders on the bike, which pretty much deals with spray from the road, and my backside protects it from above. If I need to leave it outside in the rain when I'm not riding it, I simply slip over a shower cap that I leave tucked under the saddle the rest of the time. I've had that saddle about 6 years, it's been ridden in all weathers, it's fine.