I don't know if this helps, but when I went fiberglass I didn't like the
idea of the mounts only being held by a 'glass and plywood' sandwich no
matter that  is is almost 2" thick so I plated the areas with 3/16" plate.

I drilled holes right through the floor into the plates to anchor the
plates with bolts and large washers, then drilled for the mounts.  I
managed to tie in the 'sport' bar's front mount to the plate which ties
to the frame mount to beef up it's structure.  I am still under some
construction in the rear but am going to tie the rear of the sport bar
to the frame also in the next modification.

Because my 'glass tub fits different than stock and doesn't have those
ribs, the mounts weren't the right height so I just used large washers
stacked that I sprayed with cold galvanizing to prevent rust first.  A
bunch only need one washer like stock, the rest got small stacks.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
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