Wouldn't it be easier to put some stand-offs onto the existing mounting bolts to move the speaker away from the wood mounting?
If you cut a new pair of plywood oval rings, screw the new speakers to them, and then mount this to the existing wood with some spacers you'll not have to change the car, and the only difference will be that the speaker cones are a few mm further back from the grilles. if you were concerned about leakage around the gap, you could add a simple shroud to block it off.
Last edited by Hamwich; 17/03/15 01:51 PM.
