Maybe you could use a Karvonen-style calculation, say off 100m pace as maximum pace. Do you know what I mean? Something to think about on your next elliptical workout. It's too early in the morning for me to figure out the mathematical relationship, I'll try to puzzle it out later.
Once I had to project 3.6 mile race times onto equivalent 5k times, at 5k RP NOT at 3.6 mile RP. I plunked a bunch of 5k race times into McMillan's calculator to get the equivalent 4 mile times, then did a linear interpolation of each pair to get the 3.6M time. (I used a spreadsheet.) So now I had a set of 3.6M times and associated 5k times.
Then just for curiosity I took the ratio of 3.6M time to 5k time, and was a little surprised that the ratio was constant over the paces I examined, to three decimal places. So the net result was I could just multiply the 3.6M time by that number.
Not sure what this means for easyP/10kRP....