Bill it a great idea but if his 248 is like mine (03) you wont have the inch.
I actually just took that panel apart last week to run the wiring for my windlass. Turns out that starboard panel up on the head is held on by screws that are accessed behind the mirror.
Not sure what bracket you will use to mount it but if possible I would just get screws to go through the fiberglass behind the mirror though the wood and use that to support your mount.
-w
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Walter

2003 248 Vista - VP 5.0 GXi
2009 Toyota Tundra SR5 5.7L 4x4