remix of Boots Industries filament spool holder

This is a modification of the Boots Industries (BI) filament spool holder design, published on Thingiverse. As with the original, it uses a single 608ZZ bearing, but uses a bit more 4mm hardware, in order to both clamp the bearing in place securely and to allow fine-tuning of the drag desired to govern spool rotation.
Various brands of filament have spools with different diameters of the hub hole. The BI design requires a different removable adapter piece for each different diameter, where t