I picked up the FH762SV-SCAR muzzle device from Shooting Surplus this week and got it mounted. As far as I understand this is the clone-correct device for the SCAR 20 SSR, and is why the SCAR 20's heavy barrel has the step-down notch in profile. The flash hider extends down the outside of the barrel and covers much of the notch.
There's still a small gap between the shoulders of the notch and the end of the flash hider, so I added a size 7 silicone ring to close the gap for aesthetic reasons only. To me this really helps the proportions of the front of the rifle and as everyone knows, looking cool is the most important thing in the world.
Just thought I'd post up some pictures in case anyone else is considering getting one.
I haven't had a chance to shoot it yet, but I'm assuming good flash suppression with some very minimal recoil reduction from the design of the ports. I'll report back.