Wow. This all good info. The velobase site is pretty cool (ps-the link was dead). There is no plastic washer there, though there is a metal one... perhaps I've found the culprit. I'll dig around and see if I can find something that'll work.

The whole issue is that when I tighten the lock-nut so that the arms aren't loose the calipers become too stiff to move.

Thanks for all of the input. BFers rule!