Bob,
Nice work so far. I am from the NW side of Ohio and am currently researching parts, designing, etc. for my build that will start this fall after I finish the wife' 66 GTO convertible I have been restoring. Ordering my kit in May. I have been looking for a good EPB option and may copy your Tesla calipers option. The other way I am looking to possibly go is High Spec Brakes from the UK. They make an electric spot caliper setup that is a complete system.
Nice "go-kart" session video, you are inspiring me even more!!