I bought a D2 steel one from DNT. However, the flat trigger that came with it doesn't seem to have been machined properly to actually work (or just doesn't like my lower for some reason). The lever needs to be pushed basically all the way forward to the point where it touches the hammer for it to unlock the trigger again.
Based off of research it seems like the left side, the rounded side, needs to have more material removed from it. I don't think I'm going to be able to do that with the D2 steel. So I ordered another skeletonized trigger online to modify myself. Is there a best way to cut the back of the trigger precisely so it works?