Spades are a little tricky with the QS-8s, but I found if you come in from the opposite side so that the connectors fit inside that cup shape, you can get the speakers to mount flush with the wall, even with 12awg cable which is what Im using. I found it easier to take the screw completly off the post to allow room to manuver the connectors into place.

If you need a little more explanation Ill send ya a picture of what Im talkin about.