I just realized better then wood/Tnut and much stronger. Uni-strut. It's square metal beam with locking square spring nuts. I use on my roof for a universal roof rack. Can get at home Depot. You could also use just the square nut on the back of the plywood if you chisel a little dent it will hold and you will have a stronger solution but 1/2-13 vs 1/2-20.


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2011 E70 • N55 (me)
2012 E70 • N63 (wife)