[eugenebrooks]

One could ask the GDC how thick an aluminum plate needs to be,
mounted on standoffs shown, to satisfy the letter and intent of the
rules. Do that and carry a copy of the QandA to the inspectors at
the regional just in case.

One could also make the backing plate from stacked aluminum tubing,
stacked 4130 tubing that is available as small as 3/8 square, or laminated
carbon fiber panels. The tubing would certainly be considered structural,
and the carbon fiber would also be if it were laminated thick enough.

Eugene