@Glasspack - yes I built the DART panel. Here is the schematic as promised...drew it up hastily in OmniGraffle. I had a bill of materials from the planning phase but looked it over and it doesn't represent the as-built very well so I'm not posting it.
@HonestJohn - TLDR operation tutorial:
Toggle switches are pad selectors
Insert key and turn on key switch - power light comes on.
Flip up arm switch cover and turn on switch underneath - "arm" light comes on and continuity LED will light if you have continuity
Press "Fire Missiles" button to launch
Parts - case is a Seahorse 520 (Pelican clone). There are no case penetrations so it's water- and dust-tight. Get a good key switch (I used Eaton) and an SSR. We wore out a vanilla mechanical auto relay in several thousand launches. Use E-Switch or Eaton toggles from Digi-Key. Cheapo switches will not have the life. We did use 1/4" plugs/jacks from the Amazon 20-packs. You have to solder the center stack of the plug since from the factory they are just crimped and go flaky right away, but after doing that they have been solid for 3 years. Battery life is amazing...we can do 1000 flights on 50% charge of a 3 Amp-hour LiPo.
Planned upgrades:
* brighter LEDs - the ones we have are not too good in sunlight
* add piezo "armed" buzzer in parallel with the arm LED
* (maybe) change power inlet connectors to PowerPole
* Change toggles 16-20 to spring return momentary for MPR/TARC pads to disallow multi-select