danmcclen I'm not sure if you need a centering block. (Only needed for m16 pocket cut) However to alleviate bolt bind with a metal super safety I have found that I have had to file down the top of the lever that contacts the BCG. I continue filing and testing fitment by pulling back the charging handle to see if it still sticks, once I file to the point where it no longer sticks, I polish the lever, install it, and add a drop of oil.
The highlighted green surface is the area in question.
I'm not sure whether your lower has a high shelf, but if your super safety has full motion of travel rearward then you do not need to modify the lower.
Let me know if you need anymore pictures or help. One last thing would you be able to tell us who made your SS?
