Thanks to everyone for helping me with such great ideas for failure! Keep them coming!! In the meantime, I uploaded a video of a coupler that I think has a very good chance of not working. The stock piece called a "hub" took 3 tries for me to finally buy the right size: 1 3/16". At this point, I am very angry because I was hoping to be MAKING money from this project, and here I am out $5.49 for the coupler. I feel like ripping a piece off the ICE of the Metro and putting it on eBay. I uploaded a new video. There are two setscrews there, I'm going to add another two to the motor section, then put in four for the clutch center portion to make sure it's nice and tight.