One issue I've seen with the Powermasters is that the gear does not come out far enough to fully engage the flywheel. It still works, but if there are any problems it will chew up the front half of the teeth on the flywheel. I've machined the front plate on those Powermasters so that the starter sits deeper in the opening to address this issue. It would be a good idea to check that before installation, just to see what you're dealing with.
I prefer the RobbMc starter, which does engage the teeth fully, and also has an option for a nose cone to support the shaft, rather than having the gear cantilevered out towards the flywheel when it is engaged.