OK, so after probing the fuse sockets and not finding any drop in voltage, I thought maybe it needed the headlight load in order to induce a failure. So I connected the cross jumpers I was talking about. I turned the lights on for a LOOOOONG time, both with the engine running and not running. FINALLY, the RH bulb started to fail, which told me the problem was somewhere between the fuse and the bulb. It would come on for a couple seconds when I first turned on the switch, then it would fail. After shaking the harness, playing with plugs, etc., the headlight finally went out once and for all - wouldn't come on no matter what. I thought to myself "Eureka, now I can find the problem." I probed the wire connections at the bulb and found 12V. "OK, maybe the ground point is flaky." I unplugged the wires from the bulb and checked for continuity through the bulb. "OH MY GOD! BAD BULB!!"

Somebody said early-on in this quest to replace the bulb and I ignored their advice because I had never had a bulb that would fail intermittantly like that. And for a while it was consistantly 3-5 seconds after starting the engine.

Moral - Look to the simple stuff first.

Thanks again for all your help, schematics, etc. (I've been wondering how many nested messages Jarrod designed in as a limit on the BB.)