If your objective is to mount an EoTech 552 and an optic multiplier, and a fold-down BUIS within the confines of just the receiver rail, I'm nowhere near smart enough to know how to do that. I had to mount forward railed grips so that I could push the 552 forward enough to get good access to the EoTech buttons with a BUIS installed behind it. I believe that I could install an optic multplier behind the EoTech, but there wouldn't be any room for any kind of rear sight that I'm aware of. Currently, my 552 extends approximately 2" beyond the fwd edge of the receiver rail, and there's also about 2" between the EoTech and the ARMS40L mounted behind it.
There's plenty of folks who post here that know all the options so until one of those guys checks in with some suggestions that's all I can do . Good luck.