Hours later and I’m finally learning to spell CAD and making progress.
No real measurements, just trial and error, but I finally got two couplers to mate and not bind. I printed with a brim which makes it a little bit of a pain post production. Might skip the brim in the future and see how it goes. Also had a lot of problems with supports as the part where the pin goes is the only part that touched the bed of the printer. Experimented a little and added to the bottom of the drawbar so it touches the bed as well. Not accurate, but also hard to see so I’ll take a cleaner part over absolute accuracy. 
