I printed at .3 layer height, 5 perimeters, 0 top and bottom layers and no infill. Using 0 top and bottom gives you the groove in the arms, but you can cap them if you want. 5 perimeters will make it a solid object so no infill is needed. The center bearing should press in with no fitting, but is tight to pop in, the outer bearings will probably require scraping. I use a pocket knife, scrape around a little bit to knock the ridge down, the try to push it in. The rings they fit in are cut out with a sphere, so they are wider in the middle. Just do enough so pop them in with a fair amount of force and they will stay in fine.