So I'm looking into buying a total composites box that's mounted to an aluminum flatbed. I was wondering how to run various items (toilet exhaust, heater intake/exhaust, water) through the floor? The original plan was to use a subframe and drill where the gaps are. I'm sort of lost on what to do with a flatbed? Do I drill through it? I would much prefer to have things exit through the bottom versus the sides of the box. Thanks!