Another helpful note for a convertible BAP install is that the picture in IronTerp's write up for the location of the BAP is in a coupe and that support is NOT flat in a convertible. There is a flat spot on the floor of the trunk close to the fender where you can fit the BAP and get two screws in. I used some double stick foam tape to secure it and keep it from vibrating and then used some slightly longer screws to reach the metal floor board.
Just make something like this for mounting the BAP