I had to fix some things.
After I printed it all and assembled it, I realized that I didn't make a way for you to unload the tape without disassembling it. Duh...
Now if you push the lever arm all the way back (2 degrees past where the normal stop is) it disengages both cams.
It also turns out 15mm is not a standard length for 3mm bolts. This meant that I had to choose between 14mm and 18mm. Well.. that sucks. I'm not making the whole thing thicker for a bolt, and I'm not cutting them all either.
I also compared my upper profile to a Juki nozzle and discovered I didn't have enough clearance. I'm not using an off the shelf nozzle, but I should probably plan for that.
So.. I reworked the entire design to be 1.5mm thinner so I can use the 14mm bolts, and I lowered the front cam area to clear the nozzles. While I was at it I added some tabs to retain the cover more nicely.
I'm happy. Printing again.