This could really be described as gratuitous tinkering. I made some minor adjustments to the original thing uploaded by Edventure Time. I made the interior channel more rounded, made the sides of the channel taller, and added a couple of bumps to help hold the filament in there. I also made the radius larger where it fits to the MPSM.
I printed this with supports the way Edventure Time had described, meaning that I rotated the thing 45 deg. in Cura so the support structures were not parallel to the channel at any point.
After printing I removed the supports and cleaned up the rough areas (mainly where the supports had been) with a couple of needle files. I wanted the inside of the filament channel to be smooth.