This is a perfect example of "Form Follows Function". In designing anything, you should always include some way of removing it from the surrounding environment. Making it an exact fit was a poor decision in design. At some point during assembly, you should have realized that you were going to need access to the cars systems for maintenance purposes.
I guess at this point, you need to decide on what's more important to you. A sub-woofer enclosure or a decent handling car. You may get to the point where the car decides it for you and you end with a great sounding car that is unable to move out of the driveway.
Good Luck, I think you know what you need to do. You just need to accept it.
