Nick - Just a suggestion on your positioning of the pressure brake light switch. I'd veer towards having the switch mounted straight up or at least horizontally. Up or either side is better than pointing straight down.
Pointing down like they are leaves wires potentially hanging low to get snagged by the odd bit of trash/debris your truck might drive over on the roads. An errant plastic bag or cardboard box under the truck could snag on the wires, pulling them off and/or damaging the wiring so you brake lights stop functioning.
Which of course could lead to other less than happy circumstances, like getting rear-ended by some speedy knucklehead - ARGH!!! Just thinking safety here.
