This system is designed for the low volume, high pressure rams made by AC for the system. Any time you use a large volume ram you will probably not have enough fluid. The lift arm rams are small diameter pistons you will notice.
What I have seen is aux fluid tanks mounted on top of the hyd sump on the WD with a hole drilled for gravity flow, and fittings to connect the two. Many folks here have other methods so you should get a better response from them.