Pulley troubles

My MakerBot (Batch 9) uses printed pulleys.  I had attached them to my MakerBot with the bolt going down into the body with a nut underneath.  As far as I can tell, there’s only two ways to attach the printed pulleys to a ‘bot:

  1. Bolt going down into the ‘bot, nut underneath and inside, pulley with the tapered edge on the top.
  2. Bolt going up from underneath and inside the ‘bot, nut on top, pulley with the tapered edge on the bottom.
Printed pulleys, tapered end down

Printed pulleys, tapered end down

The problem with this orientation is that the pulley can slip down on the bolt.  When this happens it’s very easy for the belt to gradually ride up the tapered edge and then right off the pulley.  This ended up killing one of my test prints as the Z-stage started to descend to start the print.  Because of the way the “tapered end up” orientation of the pulley rides on the belt, I don’t think sanding away the taper would totally remove the problem.