I'm using almost the same setup except for M14 mags. I see that you made the trigger guard shorter. For the M14 mags it looks like the guard will need to be moved back one set of holes. The problem is that the mag is in the way for the stock center support. How are you going to install the center support? I wonder if a center support made of stamped steel in the form of a H spot welded in would work? Maybe just two arms off of the lower rails bent together and spot welded after the rails are installed?