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!
I'm sorry, I missed that this is GXP!
GXP requires no spacers if you have threaded BB cups. That is because the shoulder on the spindle and the NDS arm pinch the left bearing. That prevents any lateral movement. The "play" on the right side is just to account for variations in the BB width, and doesn't need any spacers.
The reducer (part 4) absolutely needs to go from the inside as depicted, otherwise the pinching thing doesn't work and the spindle will just walk out to the left.