I have the Waffen Burk gas block for 11" barrels and I am waiting for my 11" barrel now. The only difference between the 16" and the 11" gas block is the length of the lever for the switch. The version for the 16" barrels have a switch that is longer and protrudes further forward and if you put it on an 11" barrel you won't have clearance for a suppressor. I am not sure if the MR223 11" barrel has the same size gas port as the 10.4" 416, but the barrel I requested from Nefarious Arms should be 1.6mm. The reason for this larger port size is to utilize the full range of the Waffen Burk adjustment range. So as you might have seen, the range is N+, N, SD, 1, 2. N is for normal unsuppressed use. They have an N+ setting for overgas beyond "normal" for adverse conditions. If I remember correctly from when I was modding my MPX gas block, if my gas port is too small there is no way to leverage the highest settings, and so I am applying that logic here. Im also not worried about overgassing for suppressed because there is a 1 and 2 setting for reducing gas even lower than SD (their suppressed setting). Hopefully this helps you.
Im waiting for my barrel still. Once I have that I can put it all together and test it out at the range.