I spent most of the time this evening getting a pattern completed of the firewall. Although it look pretty strange, I ended up with an exact pattern of the areas to cover. Basically, I just fitting and taping paper up against the stiffeners until I had a tight fit.
I layed the pattern on the firewall insulation material and was able to cut through it to using a razor blade. I thought I would have plenty of material, but it looks like I will just have enough.
When I have everything installed on the firewall, I'll use the 'glue' that came with the kit to permanently install the insulation.