Finally picked up a 4'x8' sheet of 1/16" thick aluminum diamond plate to build the rear belly pan and rear diffuser from.
I should be able to use some slotted angle to use as attachment points fer the multiple rubber straps that will keep the rear belly pan and diffuser tucked to the rear axle. I should also be able to install the hinges on the inside of the bend as well. There won't be any wood on this portion of the belly pan at all. I'll use some vinyl base board to isolate the aluminum from the steel so no galvanic corrosion will occur between them. I'll be upgrading to stainless steel fasteners as well.
Will it make a big difference if the diamond side faces outwards towards the ground?