I am using 1.5" thick material for my baffle. I will cut 3/4" into the baffle to flush mount, but I would like to know what diameter of the outside circle is needed to flush mount the driver. The plans for the cab on the website list that an 11" diameter circle is needed to mount the driver. If I use an 11" hole, what width of rabbet do I need? In other words, what diameter does outside circle for flush mounting need to be? 12 1/2", maybe 12 3/4"?