where is the best place to mount my battery box, is it ok to just drill through the back wall underneath the sleeper in the gooseneck area.

Is there any supports in these areas that you know of my trailer is a 2000 horton

The best place to carry a heavy object such as a battery, is where the strongest part of the forward bulkhead is located. That would be any area around the perimeter, where it joins the walls or goose flooring. The closer you can get to these joints, the stronger the construction you will find. In addition, many bulkheads are further reinforced with vertical and horizontal frame members. You can locate these if you have a finished interior by looking at the fastener patterns on the outside surface.

Use bolts, self locking nuts and large fender washers for the tray's attachment, to lessen the chances of the hardware from pulling out of the thin aluminum. Stainless fasteners are found at the big box stores. Do not use any galvanized hardware.

Gard