Wow I should have asked this question before I got started. I already had the batteries. Picked up some group 31 crown deep cycle batteries off of craigslist for $60. I was not aware that there were remote fill gadgets to top off the batteries. That makes a lot of sense. I like the idea of trap doors but i don't think I would be able to seal it well enough. The drop down brackets and pins are something I haven't thought about and would probably go that route but the simplest solution is bolt in and battery tenders or the quick fill linked below.
http://www.amazon.com/Flow-Rite-MP20...ords=Qwik-Fill
Thanks for everyone's input
Hopefully when these batteries die . The lithium ion phospate 12v batteries will get a lot cheaper.
http://www.aliexpress.com/item/4S20P...326606716.html