I've updated my VDOT calculator to support slower runners. The standard Jack Daniel's book only goes as slow as a 9:11 mile, 30:40 5K, 2:21:04 half, or 4:49:17 marathon, so I've extrapolated the values for slower runners.
For those interested in the details, I ran through all the values in the book and worked the percentage of VO2max each was using. For nearly all the VDOT levels, the percentage was always the same, with only the shorter ‘R’ paces having some variation. I took the average VO2max percentage for each training pace, then used the calculated VO2max to generate the actual times.
So far, I think the values that are calculated are reasonable. Even for a 6 hour marathon run, the Easy pace is 12:49 min/mile, which is slow, but still viable.
Let me know what you think, or if you spot any problems.