I'm starting a thread for the beta testers to capture any bugs found, work around/fixes, and any tips or lessons learned while assembling and testing the GUS Simpson.
Bug:
While assembling the arms, I found a problem with the alignment of the holes for mounting the stepper motor. It seemed like all of the holes were slightly (~0.2mm) too close to the shaft/spool opening, so I could only get one bolt to align to the threaded hole on the stepper motor. I was able to work around it by drilling the holes on the arm wider. I'm using the original lower arm that Nicholas posted in November, and I know he updated the file since, but I did not see any mention that this particular bug was addressed.
Bug:
I could not apply enough pressure to drive the bolt that anchored the guitar tuning peg to the lower arm. The arch of the gear immediately above kept me from using a hex key wrench from above, and I could not apply enough pressure from the side to drive the bolt into the arm. I ended up drilling out the hole, coating the bolt with superglue, and press fitting it into the wider hole.
This may not be a problem for everyone. I have fat fingers and was only using long nosed pliers and a simple hex key wrench. Perhaps better tools or someone more nimble hands will make this a non-issue.
Lesson Learned:
If you are going to heat up your parts in an oven in order to easily push in the bearings, DO NOT handle the arms by the split gears. The soft plastic will deform and keep the gear teeth on the two arms from aligning properly.