Reverse Bodwen (rail setup only) - uses mini pneumatic clips (Patreon)

I will see if I can make a new X motor mount for wheel setup that can accommodate the same thing

the model for PC4_M6 needs a small 9.5~10mm ptfe tube sitting between the two pneumatic pieces (PC4_M6), also it's may be needed for carve out the end of the ptfe tube in a funnel shape to help guide the filament in case of small misalignments when you feed it.

Also It's best to get larger inner diameter ptfe tubing meant for 2.8~3mm filament ( but still 4mm outer diameter) to reduce friction. Unlike a Bowden setup this is just for guiding filament cleanly.
only place to keep smaller "normal" ptfe is between the direct driver extruder and hotend.