I'm a little concerned about your insulation - it's horrendously flammable and gives off toxic fumes, I'd advise something a bit safer?
The entire car is horrendously flammable and gives off toxic fumes - some encapsulated insulation - which would usually be 2 pack expanding foam poured in between the skins - is the least of the flammable parts to be concerned about. Bear in mind that the insulation is behind the fuel tanks!!
You also have to remember the combustion triangle - These panels will be sealed, pretty well airtight and doubly so as they are fully wrapped in aluminium foil, and then sealed in a 1.2mm aluminium skin that is both rivetted and sealed. The aluminium will have to burn through before the PU gets sufficient air to burn.
As you can see here - That bulkhead filled with expanding foam is one of the few parts still fairly intact from this Litton which got a bit toasty