Sunlu S4 cradle - increased height

A cradle to minimise spools lifting off the bearings in the Sunlu S4. Rebuilt from scratch. Uses Prusa square nuts and 20mm m3 bolts. The bearing slots have been lowered as far as possible to allow for spools with larger than usual diameters. Update 03/11/24: Minor tweak to simplify square nut installation and give a bit more space for small diameter spools.