Today I finished fitting and drilling the firewall recess to the firewall. I had to do quite a bit of "massaging" of the recess with a hammer and blocks to get it to fit the firewall.
I have a sheet from Van's separate from the plans and instruction manual stating that the recess can either be riveted to the front of the firewall, or on the rear between the firewall and stiffener angles. I'd like to do the latter, to provide a smoother surface on the forward side. The instruction manual suggests not installing the recess until later to provide access for installing the rudder pedal brace, but I don't see how to get the recess between the stiffeners and firewall after the stiffeners are installed. I'll have to do some research to figure this out.
While I had the firewall parts on the bench, I went ahead and deburred all the holes, and deburred the edges of the firewall and recess. Deburring the stainless steel is much slower and tedious than aluminum!
The recess is fit to the pre-punched holes in the firewall.