I get 0.34mm and the only difference between mine and Jim's is "user constant" of 1.5 instead of 1.4. I tend to lean toward smaller with paper because blue and uv is usually so strong outdoors. The difference between .31 and .34 might be hard to detect.
Jim, I was not very clear. What I mean is that I've seen an odd almost split-toned effect on some long exposures. I was speculating that it's due to the mixture of different emulsions on VC paper. It's a puzzle: I also have some long exposures that don't show it. By long, I mean 10 to 20 minutes.
This is the most extreme example I've seen: http://www.flickr.com/photos/neds/8430730455