RF100 heavy spool hub adapter thing

Helps a large filament spool (with a 53mm central hole, 60mm deep) spin smoothly on the RF100 standard spool holder.
* A 1kg filament spool I have has a rough spindle hole and was snagging once every revolution, producing regular skipped extrusion/weak layers/horribleness in my prints.

Outer diameter is 50mm, inner is 36mm, and it is 70mm long (slips easily and securely over the standard RF100 spool holder pin). The flange is 60mm diameter and 5mm deep, allowing for a spool hub width up t