I have just incorporated a fix to the problem I was having with a belt jumping teeth on my new 3d printer build. I decided to take 2 standard skateboard bearings and mount them on the bolts used to attach the Nema 17 motor. This meant that I needed a bushing to adapt the 3mm bolt to the 5/16" hole in the bearing and create a standoff distance of 1/4" from the mounting plate. I used 2 bearings and a connector plate to stabilize the 3mm bolts. This works great as is doesn't add too much deflection to the belt and require any additional plate. The photo is a little blurry because the printer was running at the time.