Battery venting

There's nothing in the overkill NZ Rulebook about popping your hood when charging. Of course Hydrogen does rise and might get trapped under your hood. But at the same time, car bonnets are not watertight. They're full of gaps around the top. I wouldn't worry about it.
If you're concerned, why not set up a little low amp brushless fan under there to keep circulation going?

Yeah, that's what I figured. I thought about installing a fan, but I can't think of a place to put it. I guess I could put it just about anywhere, just to keep some air moving under there.

[goes outside to lower ridiculous-looking raised hood]

I'd concur. Hydrogen is the smallest, lightest, and most "slippery" of the elements, comprised of a single atom. It's difficult enough to keep it in a sealed container, any hydrogen released under the hood of a vehicle will immediately dissipate without the help of a fan. What you really want to avoid is the accumulation of hydrogen, or, more correctly, hydrogen sulfide gas, from the charging of the batteries. As long as your batteries aren't under some type of enclosure that could cause the gas to "pool up" in an inverted hollow, you can just as well forget it.

OK, thanks guys. Makes it quite a bit more convenient to charge!