Good info thank you. I'm really looking hard at a Flat Dark Earth MR920 Elite so it is good to know that one can 'jimmy' it in there. If it came down to it I could mount my 509T on my Arisaka offset mount for my Recce rifle and get a 508T or even an RMR for the 920.
..I would love to have an Agency Arms AOS set up, at least at this point, but a stripped slide costs as much as the whole MR920! Daaaanng..