Holy cow this is an old thread, but it's relevant to my current project. Did you end up trying this out?

I have a Trijicon RMR on a QD mount directly on the rail of my SBR AR. It works well with the stock I have, but if you are used to the cheek weld position of a higher sight line for irons or other optics, it takes some getting used to. I can post a pic if you want.

I am building a PCC right now and probably going to put something like a Vortex Razor on it, but I decided yesterday that I don't want it quite so low, so I'll probably go with a cowitness riser.