Re: Charger Sizing... (too big?)
Something Bill skipped over, is that all else being equal, a charger with an excess capacity rating will run cooler than one that is "just" enough. And by running cooler it should also last longer. Electronics are often derated at 1/2 life for every 10 degrees of temperature increase, so running cooler can make a big difference in the long term.
Bottom line, buy the capacity you will need, shoot a little over that, and you'll be fine. Any decent charger will handle "smaller" battery banks without a problem. Worry more about the installation (proper ventilation and cooling, keeping water away, proper cabling) itself.