Flexi-friendly extruder

Derived from original design, to add 4mm holes for filament to insert 4x2 PTFE tubing.

This is specifically designed to easily print flexible / rubber materials. The idea of the two PTFE allows to create a "almost uninterrupted" path for the filament around the MK7 direct drive pulley.

STL now have supports so no need for extreme bridges like in the photo.