The biggest disadvantage is the loss of db'zzz. If max SPL is what your trying to get out of your equipment then get that sub in the trunk or keep it in the back and wall it off ;-) Perfect example I used the same exact gear I used to register a 150+ (legal n TL) and tried to fit it into a volvo's trunk. It didn't fit and was the day before a comp. so I put it in the back seat and barely hit a 144 and that was after I put my huge external port into the trunk, at first I had the port basically pointed at the sensor and registered UNDER a 143.