Most of the time you can remove your recessed battery on the tongue area and mount some angle strips on top of the tongue area and extend out on both sides of the tongue.
This is what I did here with my setup... I can add as many as four batteries across the trailer tongue doing this...
Adding batteries will increase your tongue weight however... Sometimes folks have to move their propane closer to the front tongue jack...
TORKLIFT also carries a line of battery hangers where you can mount the batteries under the trailer as well...
Pictures would help...
Roy Ken