I went ahead and installed the heat box. This still needs a cable run, which pains me because my panel is nearing completion and I don’t know where this and a few other runs (alt air) will penetrate.

The hole in the firewall proved to be a bit tricky to add, but a brand new hole saw took care of it after a few failed attempts with other tools.

While I was at it, I went ahead and added the firewall recess.
Not pictures are available, but I completed the brake fluid line runs, and torqued down the pedals. Side from the rudder linkage and final exterior brake line runs, these pedals are ready for action. I won’t add fluid, likely, until I’m in a hanger.