For grins, I went back and did a VAM calculation off a PR on a 13 mile, 3200 ft climb. The timing of the PR was a few months after a professionally done test at a cycling clinic. 930 VAM, based on a real world, hour long climb came out at almost exactly the same place as the earlier test (20 mins) in terms of FTP (280) and watts/kg (3.8). My sense is in the four hard years that have passed, I would have trouble hitting 75% of that mark. Oh well.