>> Something is not adding up in my head, which I'm guessing is 90% me not understanding how you >> run and maaaybe 10% something about your running. Running slower often causes people to bounce, >> yes, but then generally the body chooses to be lazy and that slowly smoothes out the bouncing >> over time.

Try running a 14:00 pace with a ruck sack. I would bet that's close what I'm trying to say here. There is this sweet spot where any slower doesn't feel any less tiring because I can't make gravity be any slower.

I don't understand "But I would expect your running progress to be very slow (whereas your aerobic response would be excellent)." My aerobic response is the limiting factor here. So maybe this is something you can help me understand?