I read another thread where a guy mounted a Shield Arms RMSc and had to shim the rear of the dot. Apparently with those dots you have to mill the slide with a 1 degree cant forward.
That fella also mentioned he was not happy with how his was milled, he believes it was a mistake on the part of the machinist.
My RMSc was milled parallel with the slide, by Primary Machine, and I have plenty of adjustment in all directions. My 1* shim remains in my original packaging.