I knew getting the pulleys to align properly would be a challenge and crucial for proper operation of the Rotrex. Misalignment can result in belt wear/failure and slippage.  Since I'm only using a 6-rib this must be spot on.

I read in a MP90 install-thread somewhere on m.net that Gates has a tool for doing this accurately.
Say hello to the Gates Drive Align laser tool :

Rockauto.com sells this for $85  compared to $139 on other stores including eBay.

Easy to use but remember to calibrate the unit with the included template before starting the light show.
My manual preliminary alignment with the straight ruler and spirit level was way off.

In action: