If you're like me you probably have more 608 bearings than sense. This design puts angular contact on the spool edges so it'll always be aligned and smooth-rolling with no complicated spacing mechanisms. Print two of these and enjoy luxurious, spool-width agnostic, weirdly shaped rolling support. Prints without supports, whatever infill you like. I used 20%, it's really not critical. Overhang is slight, the bearings just need to slide on.