I'm going to pick up a good set of hex tools in the next couple days. In the meantime, I thought about how the grub screw is rounded on the bottom and decided to keep it that way and mill a divot into the motor shaft. This motor is dedicated to this truck so I felt ok doing it. I used my milling bits and my benchtop drill and put a nice little divot in there. The grub screw sits down in there nice and I put on some red locker. I'll see what happens once that's dried.