I think I know whats going on here, Mr Mike made me a pair and the grub screw was further up on the coupler than it needed to be. I had to send them back for him to tap a new hole closer to the end.
Contact Mike via email or PM and I'm sure he'll happily remedy the problem.
Looking at your picture - this seems to be the answer.
Hmmm. Your couplers really look a bit different than the ones I got from Mike. The ones I bought fit very nicely on my LST output shafts. Just a little tight but they fit fine and the grub screw was in the right place. Bondo might have the best explanation to what happened. Like it was said, contact Mike and tell him about your problem. I know it is disapointing to have to wait again for parts but it will be worth it.