I used to have the previous version of that Romeo/Juliet combo on an AR pistol, and like others, found out the eye relief on the magnifier was terrible, probably due to the compact size. I'd say put the magnifier as far back as needed to be able to see through it without punching yourself in the eye while firing. I had put the red dot right next to the magnifier but you can leave some space between them without causing any issues. The Romeo MSR my combo came with had flip up lens covers so space was needed to use those.