How should the REM firewall pad be cut at the ac opening? Should I cut the pad the same as the existing rectangular firewall hole? and let the heat/cool air distribution box smash the pad around the box's outer edge when tightened? Or do I need to cut the pad where the outside diameter of the air distribution box is not touching the pad?

The flange on the box uses the dash mat as its gasket, and compresses it. graemlins/thumbsup.gif

Awesome!