Swede,
I had four setscrews to hold the clutch center. It is becoming quite obvious that welding will be necessary. I thought all the lovely grinding noises I was getting was from the fact that the coupler was not held in place by anything: it was free-floating between the motor and the transmission (Could also be some flexing of the thin 1/8 inch steel I was using for an adapter plate).In reality, it seems that the coupler was in there pretty snug. The grinding was apparently the setscrews giving way. The larger setscrews connecting the hub to the female motor shaft piece were holding under the low load conditions. I'm guessing it should all be welded together and I could then put four setscrews to try to secure the new "one piece" coupler to the motor shaft. Ok, I doubt anything I said made sense: I have a hard time expressing myself. Here's a video, it makes more sense than my yammerings: