Not a hundo on all your q's, but here's some suggestions.
Check the length of screws, relative to the ski.
Double-Check the length of screws, relative to the ski.
Cutting Boards seem to be the homemade riser of choice, make sure it's not a brittle material, hell whomp the shit out of it in the store, see what happens.
7mm seems like it would be adequate, double check by measuring the exposed screw under the binding and see what you come up with.
I would really recommend using binding screws and not some run of the mill stuff from Home depot.
The binding screws will have a posi-drive head, meaning it is typically a thicker gauge, and stronger head, less likely to strip, and or break.
Want to see pics of this thing, should be interesting.
Good luck.
Skiing, where my mind is even if my body isn't.
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