Doesn't work - Strike Industries SI-AR-15/M16 Receiver Extension with QD Endplate

Maybe it's my lower (not quite your standard form lower), but I can't attach the QD to any of the three holes in the plate. The left and right holes don't have enough clearance to fit the socket in there, and the middle hole isn't deep enough to allow the retention balls to engage. Unusable; buying a Bravo Company replacement. Don't both try saving a few bucks with this POS.