The box will hold it the same way it holds a regular mounted speaker. This will increase your box's displacement since the basket and magnet will no longer be taking up room on the inside of the box. But this will take up more room in the trunk since the basket and magnets are sticking out on the outside. I dont know if I am reading it correctly, but if you want one mounted regularly and another mounted invertly...you will have to wire the inverted one the opposite way (IIRC).

Is it worth doing, no. h: