Yeah, the thing is, I've ridden this distance (400k) in these shorts with this saddle several times and been fine; on this ride I felt pretty bad fairly early on -- like less than 100k in, when that's a distance I do in this setup all the time. Part of the issue is it's not an every-time thing, so I'm not sure what all the factors in play are. Like, this is a three times in 5 years of randonneuring thing, but this time it derailed a ride I was really excited about.

Saddle is definitely under my sit bones, and is generally really comfortable, and my shorts all have the Terry flex air or fleet air, which I think is plenty or even more padding than I need -- my tri-shorts are literally just some fleece, and that's OK for 125 miles, but not more. I'm thinking maybe I should try the Desoto 400 mile shorts, which are a 4mm pad, but they're $160, which is a lot for an experiment.