Well this evening I had planned to work on the power coupling...but it seems I have lost the faceplate! Good news is that the part is currently available....but its a bit beyond my budget right now.
So, we moved on to other things and I decided it was time to get the center foot casters mounted and finished up.
While this doesn't look like much of a chore, the real trick is lining up the caster so that the holes that connect to the top structure pass through. It seems no matter where you hope to drill, you have to deal with how close you come to the raised edge that holds the bearings.
After figuring out the best locations that work for tire clearance and not drilling into the bearings, here's the end result!