What a difference an inch makes.

MileHighDart said

I hear what your all sayin'.
Kinda wasn't thinking about crash ability when doing this. Was just trying to find a quick solution without all the cutting, welding, grinding, etc, of building supports from metal.
But I'm thinking now I'll get some 1x1 square tubing and weld up a better support system. I do have some serious braces underneath welded to the bottom of the floor so that part is done anyway.
Thanks y'all

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Good deal. BTW, grade 5 is all that was ever required for SCCA racing seat hardware. Grade 5 has shear strength 80% of a grade 8, and the real issue is the tearout of the floor. Sounds like you have that covered, OP. Once you get some tubing under there, the bolt will be in double-shear, the force on the floor will not be as much in tear-out mode, and it will be all better all around.

I elevated some seats in a trucks once by 4".. .used 2"x4" rectangular tubing under each rail, with 3/16" wall; huge washers under the floor. They were not going any where without part of the floor. LOL