[bolster]

It shouldn't be hard to at lease add an ambi safety and mag release to the XCR, since those were on the prototype. I imagine the upper receiver would be more work, and probably wouldn't be necessary, as it does have a shell deflector and ejects forward.

 

[bolster]

Is it end-user installable?

If so I'll have to order one.

As long as you have a screw driver or hex key (depending on what grip/screw you're running) you should be able to install an ambi safety/selector. It is very much like the setup in an AR.