Although the battery may be rated at 200Ah, you shouldn't regularly run a deep cycle battery below 50% (or 12.06 volts), so in reality you have 100Ah "usable" for your trailer.
I just finished a reprogram and battery test using my Trimetric monitor to find my ACTUAL Ah capacity on my 3 year old Interstate group 29s. I ran the batts down over about 28 hours to 12.06V and recorded the Ah used. It was right at 125Ah. So my total capacity is 250Ah and 125Ah usable. I reprogrammed my Trimetric using this actual performance.
Interstate does not rate their "hybrid" marine deep cycle batts by Ah, so I finally got around to working the performance numbers. I had swagged the initial programming number to 90Ah......now I know why when I was at 40% charge on the monitor, I was still at 12.2V
"If the women don't find you handsome, they should at least find you handy." - Red Green