i would agree you have a draw on the system. I would also put a main battery kill switch on it, this way you know nothing is drawing it down and when you trickle charge it you will not be putting any power into the system.
Stinger 720 or the Stinger 925 very good product and not to heavy and well priced too $140 on the Net for the 720. I did 2 720 on my Maverick and 2 925 in my Commander but 2 925 is to much power and weight 2 720 is perfect. In my Maverick I installed them in the stock location and another under the driver seat with a Stinger Battery Isolator.