The moto matic pulley was like this one that mars designed. It put too much pressure on the fixed cheek of the rear pulley and eventually broke it. Also there are the issues with alignment that were brought up. making a rear clutch work on a hobbit is as easy as using an urban express input shaft and grabbing a special seal. You can even make a one way bearing work if you make a spacer for an hfl1616. Naz helped figure all this out and did all the machine work to get the hobbit crank to work with a doppler var. He has done it a few different ways over the years and the last iteration was by far the best and easiest way to get oversized pulleys and a rear clutch.