[EricH]

How many shots on one tank of air?

I take it that the light and horns are used as a warning system, not just for the cool factor. If so, a wise move.

Also a wise move to not use a PVC tank; see the other threads this summer...

Are the batteries wired in series or in parallel (this can affect charging/performance)?

I see a lot of straps holding things down; are there plans to make those mounts a bit more permanent? If there's any recoil, you may want that...

The wiring up top seems to be following the "spaghetti" plan of organization; that should probably be neatened up eventually (good practice for the electrical team...).

Overall, a pretty good design.