Thanks all. Except Stapfam.
I suspect that my spin work-outs might be actually too high intensity for my goals.
OTOH, on group rides I can hang EXCEPT high-intensity moments, ie. testosterone-fest hill-climbing when I get dropped like a rock. I'm hoping the HIT helps when I do group rides.
BTW, does anyone know how to take a work-out off Ascent and post them here? SKT generates some nice graphs, but I haven't figured out how to do it yet, and I never refer to the "help" drop-down of a program.