Thanks, Jörg, everybody,
The solution for me was to use the preset for GM Drum Kit. That's the preset #1 in Trigger Finger defaults.
I had been using the preset, that came with the defaults, called "Ableton Live Setup". I guess that's set up to work mainly with Impulse. Anyway, I have got it going. The key is to choose the preset that's "GM Drum Kit", and of course, do all the other stuff Jörg described, if you haven't already.
Until drum racks, I'd been using preset # 16, "Unassigned - Use for MIDI Learn", and all my sets of the past few years rely on those knob assignments. So maybe I'll make a preset that uses the same knob/fader assignments as #16, but the same pads as GM Drum Kit.