I've been running the aquamist 2d water injection system for over a year now. I don't think i would ever run without it. I had given thought to running nitrious before I went to water injection, but through research found that adding 50% methanol to the water gave me more power, (ie; meth is fuel and meth burns colder) .
If it's just having room for your new battery, that's easy, mount your pump in the fender and attatch it to the bottom of the metal plate that your battery sits on, there it is protected from the severe conditions in the engine bay and will last much longer.