I currently have a 450/400 3" being built on a J.P. Sauer 12ga SxS. In discussing the build, asked the builder to dovetail the rib so that I could use the Trijicon RMR mount. Specifically, the RM57. He has the mount in hand (took me about 6 weeks to get it from Trijicon).

My 'quandry' now is which RMR to use. I'm leaning toward the RM06 with the adjustable LED and 3.25 MOA red dot, though the thought of batteries in optics is somewhat unappealing. Over the weekend I saw a clip where Ivan Carter has a RMR mounted on one of his Heyms. He appears to be using the dual-illuminated version. Unfortunately, from I can gather from Trijicon's web site, the smallest dot on the dual-illuminated version is a 7 MOA YELLOW dot and twice the size as the adjustable LED version. For Ivan's 577 or 600 NE 'stoppers' this may be fine, but for my 450/400 NE, I think that dot is too big. (3.25 MOA @ 50yds = ~ 1.66" whereas 7 MOA at the same distance is 3.5")