Thanks for the info. I'd worked out a starting time of 17 minutes using the same dilution and temperature you used, so it looks like our convoluted thought processes are fairly well aligned.
Unfortunately, spinal issues are taking precedence over artistic issues at this time, so I probably won't get a chance to shoot anything this weekend. That's a shame, as there's a wonderful fog outside right now that I'd love to try to capture in the trees nearby. Such is life!