I designed a top mount for the filament spool and then I needed a way to feed the filament into the extruder without it getting caught or snagged or anything. With a little extra PTFE I put this together relatively quickly.
Be sure to check out my other object, the top spool mount.
As a note, this is designed for standard 2mm interior, 4mm exterior PTFE. You'll need ab out 5-6 inches of it for this. It can be mounted with the same M3 screws that are on top of the towers already, and it leaves a hole for adjusting belt tension without removing this part. Hope you like it!
Generally, this should be printed upside down. I think some support is needed, but you can probably do without interior support, as long as you take some time to clean up the inside of the PTFE holding loops. once the PTFE is fed through, it can stay and the filament will run through it just fine. Just make sure to not "crush" or "fold" the PTFE so the filament can still run through it okay.