Originally Posted by rzbill
I have seen the results of a fuel fed engine compartment fire on an RV (not mine).
Do not be concerned with aluminum firewall rivets.
The heat of the fire will follow the normal airflow pattern to exit at the bottom of the cowl.
DO be concerned with the aluminum floorboards under the rudder pedals.
On the observed craft, there was a melted hole in that area.
It has been suggested to cover some of the bottom skin with stainless.
While I have not done it (the suggestion was post construction), I think it is a good thing to consider.
This reasoning is precisely why I chose to fabricate a SS cowl exit ramp for my RV-8, and it's backed up with fiberfrax ceramic insulation. The reasoning here is that a fuel fed FWF fire will result in flames and heat underneath the airframe. The stainless exit ram and insulation will hopefully provide some protection to the forward floor and my feet. I also elected to follow Dan H's advice and insulate the engine side of my firewall with fiberfrax covered with stainless foil.