Hi there! Sorry for reviving this old-ish thread but...

I'm having the exact same issues as you with the Glider! Just switched from a Terry Butterfly to the SMP Glider and after the first ride (only 40-60mins in the saddle), my sitbones were sore for two days or so - particularly the left side, yet not so much the right It was tender to touch for at least two days. While it hasn't bothered me that much on the actual rides, but then again, I haven't done any 50 or 100 milers like you, it is noticeably sore after I hop off.

Went for a longer ride yesterday and while they are still a teeny bit sore, the sitbones were not in as much pain as before.

Is there a 'getting used to' period to this saddle? Are you having better luck with it now? I ought to 'suck it up' though, it is by far the most comfortable saddle I've ridden in and the only one which hasn't squashed my soft tissues so I suppose I shouldn't complain But I sure could do without sore sitbones!