....I'll try to keep this short
My old speakers were shot as was the piece of masonite that they were mounted to. So I pried up the old piece of masonite and slid it out of the vinyl 'sleeve' in the rear desk upholstery.
I then left everything in place and cut a piece of luan plywood to the exact dimensions, glued some grey indoor/outdoor carpet to the top of that and mounted my new speakers.
Then, I simply set the entire assembly back in place on top of the original upholstery, the speaker magnets for the new 4x6 speakers were centered over the existing holes.
But, since the deck is now roughly 5/16" higher, the very center of my newly cut piece is sitting proud of the shelf lip by about 1/16". I can press it down slightly with my fingers but it keeps popping back up. Hence, the need for a small screw to hold it down.
Does this make sense?
Thanks,
Chris