I have only had one problem with shoulder spacing , it was with .357sig cases. I was making .357sig from .40s&w 1X cases and had to take .011" off of the rcbs shell holder . The rcbs die set work perfectly on the case after the adjustment,
SS you have way more patience than I do. I would have given up on the MEC press and had a Dillion mounted on my bench by now. Instead you have more cool gauges and measurement tools in your possession.