Great explanation on the pinning Bubba and thanks as well for the advice on my gasser. Brendon, one thought on pinning. I always pin my firewalls as well. One thing I started doing some time ago was to use roll pins. You drill the sides just like Bubba instructed but use 1/8" metal roll pins that you can get at Home Depot. Even though they are metal they are hollow and weigh about the same as hard wood dowels. When you drive them in they compress and trust me, they aren't coming out unless you want them to. If you ever decide to make changes to the firewall like a different engine that you need to shorten the box for, You can remove them with an e-z out or thread a wood screw into them and work them out with pliers. Either method will give you the added strenght you're after.

Best of luck on your reflight.
Rod