well nuts - After reading the comments, I think I need that spacer - adapter deal. When I remove the NDS crank arm, there's quite a bit play on the free end. I measured the spindle sticking out and it's about 21.5 or so. The little sleeve-spacer-adapter slips nicely over it and takes up the play.
But it's supposed to be INSIDE that external bearing. And I do not have the right size wrench for that thing - so I'll have to see if my LBS will re-loan me the tool. ugh. . . .

man! -- square taper for-ever!