Last week I installed a pair of Rockford Fosgate 3.5 Punch speakers as rear speakers in a 2006 Miata. I did have to modify the mounding bracket #66-950C. Three inch speakers would have fit much easier than 3.5. I also had to modify the convertible latch bracket to have enough room for the left speaker. The sound is good, but I think I would look for a pair of 3 inch speakers next time. I spent as much time modifying the bracket than removing the plastic interior part.

 

Fulmerr's blog ITT.

 

car audio is never a bolt in operation, especially if you are amplifying.