I mean, nothing else goes between the bars and roof…so why not?
Just not sure I like the idea of extending and running all those (most important) wires up to the roof. Could get hooked by a branch or? You could make some sort of tube to use as a conduit, but then you run the risk of wire chaffing where you can't see it?
Then you're mounting it directly to the roof, so if,
when you end up on the lid, you have a good chance of smacking the panel the ecu is mounted to on a rock, which will kill the ecu. Even just a decent flop might not be good. Rubber mounting may help, but you're only working with 1.5" space.
How you going to water proof it in that small of a space? It will be getting blasted with water on the trailer. Actually, any rain storm on the trailer at 65 will be 10x's worse than any down pour on the trail anyway.
I might be able to slip something waterproof under a seat. But the “glove box” area is right on the drip edge of the roof. So it would need waterproofed and placed in a way that it doesn’t just splash water all over the inside.
For one, build a gutter into the leading edge of your roof, most guys just bend a ~120* or so lip on the front. You'll appreciate it the next time you're sitting there waiting for the guy in front of you and you're not getting a mini waterfall in your lap
Also, an ammo can is sealed, that's the point.... The only issue would obviously be sealing the hole for the harness to come in, I always figured just go in on the bottom and use a rubber grommit, should work for everything but being submerged for a long time. I had my ARB compressor mounted inside one that was in the bed of my last rig.
There is obviously other waterproof containers to choose from. Maybe one of the HF pelican wannabes?