Narrower Ultimate Spool Holder

I modified the length of the rails and rollers from the original design so that I could fit five of them into a drybox.  Tested and works with Polymaker and Overture 1kg spools.  Will probably work fine with other 1kg spools.

All other printing and assembly instructions are the same as the original model.

Shortened the length of the rails and rollers to reduce the total width of each spool holder.