[Rich A]

Samwood,
If you look at all the different Cobra frames on the market and look at the rear of all the frames there really isn't much impact protection there.
Now think of how many of these manufactures use fiberglass to make their trunks/complete bodies!
How much impact protection does fiberglass provide?
Factory Five uses .040" thick aluminum panels on all floor panels including the trunk.
Now think, IF fuel should leaks out of the tank and splash on the underside of the Cobra and ignite which would burn faster fiberglass or aluminum?
I know which one!

Bottom line it your choice!