Resident CQC nerd here.
It can't be suppressed with the 16" barrel since the threads are actually underneath the rail system. I was able to do it by throwing an 18" barrel on + Ratworx threading adapter. That got me out just far enough to mount a Surefire brake. I did have to drill out the adverse port on the gas regulator in order to get it to function 100%. This basically turned the adverse setting into the suppressed setting.
This is a slightly older picture. I moved the light so that it is on the right side rail, bezel end flush with the Surefire brake. This way I can take the whole rail off easily without having to disconnect the pressure switch.
For a sling, I'm using some kind of VTAC sling mount that puts the QD pount on the left side of the gun, right behind the VFG. Personally wouldn't recommend single point on something so heavy, but that's just my preference.