Update: this morning, our training group did reconnaissance on a course we're racing in three weeks. It's similar to my 30 mile, but 1/3 of the length: pretty, nice roads, gentle hills.

The gearing suggestion made a huge difference. I only went up to the big ring once, very briefly. Even tried the little front ring! Focused on cadence, rather than raw (mashing) power. Soooo much better. Far less tired, cruised up hills, still a weenie on downhills, didn't want the ride to be over. And the professional fitting seems to have paid off, too: not a tweak of discomfort anywhere!

I think I need a couple of more rides before I completely adapt, but I feel much happier and more confident after today.