I use the 40mm sum-c on my M2 all the time and have had no problems. Maybe I'm just not as picky as others in regards to these things, but I tend to just use the 50mm framelines (rather than use the 35mm frames and try to guess what will be cut off) and know I will wind up with a slightly wider image than the one I am seeing--then I crop if need be. It's not a perfect solution, but it works well for me.