I want to buy something different as I already have all of my bases covered and I'm deciding between the Five Seven and a G40 MOS...either with a Trijicon RMR. I like the idea of a flat shooting fast pistol round with exceptional accuracy with the RMR. Are there any good mounts out there?  One that doesn't hang the optic beyond the back of the slide?  Thanks!

This "looks" like what I want...with no idea of quality.  Also...slide velocity appears much higher than most traditional calibers. Anyone have issues with RDS on a Five Seven?

http://fivesevenreddot.com/products/trijicon-rmr-mount

Any sources or cites for the function problems. I'm not doubting you...I would just like to read more about it. The Five Seven seems like the ideal candidate for a red dot sight, sans any function issues. The slide is light and appears to have a high velocity, so small weight changes would likely have a greater effect.