Attaching PG71 to arm

Our team is looking for ways to attach a PG71 gearmotor to a metal bar, like a c-channel. We could use that to manipulate the bridge. This is our best solution because we are near our length limit and we don’t want to shorten the robot.

The best solution we have is to buy a 10mm hub and the machine key. Do we need a retaining clip? I need to know this because I can’t find the retaining clip and we need to order the parts soon.

The best thing would be to drill and tap a couple set screws into the hub.