Finally put a water tank under the trailer. I located it just ahead of the axle as far to the passenger side as possible to counter act the unavoidable weights already on the drivers side. This is where the fill tube was located on the drivers side.
I did have to put a drop in the fill tube to get under and around the frame side rail, but I included a simple drain in this lower section so it can be drained at any time, be it for winter, or to avoid collection of stale water.