dobo, welcome to the site!I don't remember anyone using the Mazda sub.There are a couple of thread though about mounting a sub where the spare tire goes.In
http://forums.genvibe.com/zerothread?id=4592, wildvibe asked a similar question, but got no replies. That was in June, and he said he was going to be working on one, but don;t remember hearing any results.In
http://forums.genvibe.com/zerothread?id=4520, there are some pics of pissedoffgokart's sub install, which looks like he modified the rear deck and had the subs extend into the spare area. Seems like a good place to mount one, especially to not lose cargo space (I like having cargo space), Not sure what the effect would be on sound volume/quality if you buried it below the rear plastic deck, or maybe threw a cargo mat over it too. If you do get too much of an effect from the cargo deck, it might help to remove the panels in the rear side storage areas (the ones that provide access to the rear light asemblies) like ports to the underdeck area.