Something that has always annoyed me is the spring loaded clamp that holds the bearing against the inside of the spool. If I take it off and have to reinstall it, I feel like I may chip the acrylic slot lips if I try to force it to slide into place. Especially if I'm in a hurry. Looking at it carefully I realized the spring wasn't really a good idea. All that was needed was lock washer to give you some feedback as you tighten plastic pieces together. Once you start re-engineering an assembly other improvements occur to you so here we are: What you see there is a custom thumbscrew to make adjusting the position of the clamp much easier without tools. It goes into a pair of plain washers that are sandwiching a split lockwasher. I also redesigned the "spool clamp spring" to be nice and smooth to the touch. The two stl files are attached. For each spool holder you'll need two M4 plain washers an M4 lockwasher, and an M4x40 flathead screw.