I think I finally beat this gremlin. I'm posting just in case this thread comes up in a search for someone else, it might give them one little thing to check and maybe save them some of the headache I suffered.
I figured, in desperation, that I'd replace the plug to see if I could stem this leak. Off I went to the Harley rape shop (which actually wasn't bad - three plugs and a quart of Redline Shockproof for under thirty bucks. And the parts guys were all smart AND friendly!)
I yanked the drain plug, and refilled, threw some tape on the threads, and threw the new one in.
Buttoned it up, went for a ride, and no leaky. The Redline is pink, so it's easy to see. Two days later I had a spot the size of a dime (much smaller than it was), and it was golden, the color of the old fluid. I think I didn't clean up the frame and trans and shit when I replaced the plug, so I did it then, and vowed to keep watching. Two days after that (today) I have a nice, dry shop floor under that trans.
Keep reading, the interesting part is coming up...
Here's the thing I found. I couldn't believe the drain plug was to blame. So I was looking at it. It looks like the magnet in the plug sort of backs up to the spot you'd put an Allen key in to turn it, and it's sort of staked in there. My magnet, on the end of the plug, is noticeably bent. Not bad, but if you're looking for it, you see it. I know I never dropped it, so it had to be made wrong, or suffered damage at the factory. The oil was getting in behind the magnet, and then out the staked spot in the Allen key slot. Never thought in all my days I'd see something weird like that.
So, a boring solution for a slight inconvenience of a problem, I guess.
-L.