Tommy, I use a "WELLER" soldering gun and make special shapes out of small copper tubeing to cut out the foam. It re-fuses the foam cells back together and makes it strong again.

I'm planning to use 2 firewalls, similar to the way rryman did it, but the rear firewall will be a perimeter frame (like some giant scale cowls are mounted) glued to the nacelle and the actual firewall will be bolted to this frame.

Hope this helps,

Gunny