Nothing much to show for my efforts(or lack there of) today. What time I spent on it, I spent figuring out how to get the splined female part of the clutch disk/coupler down deep enough so that all of it is in contact with the male trans (wait, what did you just call me?!) input shaft. As shown above, it would barely be in contact with the input shaft.
I've got it figured out, though. Will have to make a run out tomorrow morning to buy another piece to add to the coupler and make it noticeably longer.
Also pondering beefing up the almost too short 3/8" studs coming out of the motor. Barely long enough to get nuts on all the way. Doesn't leave anything left for lock washers.
Both issues would might have been avoided, if I had settled on 1/2" aluminum instead of 3/4".
Oh well. It's more work, but everything will be beefier this way...