To help maximize available real estate inside, we installed a new fresh water tank underneath by the axle rather than inside in the front per the original floor plan. We also added a large gray water tank underneath on the other side of the axle. Our plan is to avoid a black water tank by installing a composting toilet. (We’ll let you know how that works out.) The tanks hang no lower than the axle and are protected by galvanized steel boxes. They will be lower than the belly pan. We also had a holder for a spare tire welded under the frame towards the front.