We replaced the miserable gel batteries that used to come standard in Huskys with J-16 Odyssey batteries, in the stock location. Pretty much a simple bolt in, and they cranked fine....much better than those gel batteries, anyway. Never had a problem with an Odyssey battery not starting an engine, and I've used them a lot on both work and personal planes.
I believe that the EarthX recommendation is that they be vented to the outside if mounted inside the cabin. No need to vent if mounted outside the cabin, apparently. In time, I suspect these will be the ultimate battery. I think I'd be waiting a while until they have a track record in actual use. Sounds like they could be the cat's meow, but I'm one of those lucky dudes who's had a NiCad battery go into thermal runaway, so a little skeptical.
MTV