Ball return for direct drive printers

Recent direct drive extruder printers mount the spooler for the filament spool on the cantilevered top (as is the case with my brand new Elegoo Neptune 3 Pro that arrived with the new year!)
This constructive choice exposes the entire gantry to the risk of amplification of the vibrations of the zeta axis, with a decline in print quality, due to the considerable masses exposed and the lack of effective structural stiffening which are rather rare in small format printers.
Hence my idea of taking the filament spool elsewhere, using one of the many spooler holders with bearings that can be found on the net (i.e. https://www.thingiverse.com/thing:3876831), and inserting the original spool pin instead of a new filament return element in the upper part of the gantry, able to favor the omnidirectional dragging of the filament, towards the filament presence sensor and then towards the extrusion head which moves along the x axis.
For my new Elegoo Neptune 3 Pro printer I therefore designed the system consisting of a double sphere concentric spherical transmission, which I completed by inserting a small standard Teflon tube (10 mm) in the central hole to allow the lowest possible friction on the filament during scrolling. The connection shaft is designed for the Elegoo Neptune 3 Pro and is a standard thread M30x1.5x10 mm.
Print with 4 contour walls and with layers not exceeding 0.2 mm, in 1:1 scale to ensure correct clearances for print en place.