Low profile Spool holder with Scale

Updates
01/06/2021
I replaced the Top Spool Holder with a slight variation that requires a little less support material when printed on end. Makes no real difference for those printing flat.

31/05/2021
I added a small safety feature to the top holder to test out. Its two small posts that screw into the side of the upper piece. They provide some side support in case the spool tips on its side. I used a small M3 threaded rod to tie the posts at the top, through the centre hole of the spool. This should also hold the spool from rolling off the holder. Of course the holder has to be held in place so that it does not slide. You could also just insert a short piece of coat hanger wire with one end bent at a 90 degree angle. If it slips out of the other side holder, put a small bend in the other side to provide a little friction, so it won't slide out easily.
I have not tested this other than to put it on while doing my last few prints. I haven't tried it while the filament has been ca