Looks great.
I tested my 12 mags at the range this past weekend and they all worked great for bolt hold open functionality. I had to cut the bolt release actuation tab a touch shorter than I had it, but got them all tweaked in and feeding every single round from the mag before locking back.
The mags all fed, although I did have two double feeds and two instances of the rounds not being pushed up (stuck down). I think it was due to loading (not getting the rounds pushed back fully when loading) moreso than the mags themselves, because at all other times the mags fed perfectly.
They were tested doing fast movement and position drills for 3gun and went through hundreds of rounds.