The NASA CC&R's are a bit vague on proper attachment of a 5 point harness (Specifically the side and submarine belts). Section 15.5.6 reads "Large diameter washers should be used to spread the load. Boliting through floor panels, etc. is not acceptable without required washers".

There is really nothing else specifically about the washers. I'm remounting my belts this weekend so I stopped by the hardware store. They had 2" square steel plate washers, 1/8" thick.

Would that be sufficient or do I need a larger plate/washer?

 

that'll be good enough. the typical backing washers are 1/8" 2" diameter steel. just drill thru the floorpan and also use either a "lock" washer or nylon tightening nut. you can call ken myers at ioport, he does a lot of tech inspections for NASA.

 

For additional info-take a look at the mounting drawing that is in the Simpson catalog. Also for added strength try using the huge washers on both side of the floor pan-this will help spread the load a bit more evenly.

 

I assume that you've checked to see if you can use snap-in ends and eyebolts in any OEM seatbelt holes that might be there? There were so many stupid stock belt combinations over the years, this might not be an option in your case...

K