I uploaded the quilted top and bottom plates if anyone would like them. https://www.youmagine.com/designs/quilted-top-and-bottom-for-jetson-tk1-case-by-tonyvr
I like this design much better than the original feeder -- more open and easier to keep clean, adjust, replace the shaft, etc.
I had some trouble with this design getting enough tension on the idler to feed without slipping (still slipped and did not get any knocking or grinding even at the tightest).
Looking at the original feeder, the spring is applying pressure via a lever arm, which gave the idler bearing more pressure (and less linear motion). This design is linear so the same spring would need more compression / distance to apply the equivalent force.
I tried using a stronger spring, but I snapped the feeder arm in half (ABS) -- right at the screw. (rotating the captive nut 30' would give it a tiny bit more strength, but it would need more than that for a stronger spring)
I also had the snap-on-filament guide break on the top clip.
I considered an alteration of using 3mm hex standoffs instead of 3mm screws -- the standoffs would screw into the motor and hold it in place, then the feeder body would screw into the standoffs. That way one could remove the feeder without having the motor drop out. It does push the feeder body away from the motor by a bit, but the motor shaft is plenty long enough.
