adding more batteries

Mick.....I've seen it done two ways. One....they mount them behind the grill on the frame. The only issue, you have to run a lot of wiring. Second, my neighbor just did the upgrade that you want to do. He did it on his Fleetwood Fiesta with the batteries mounted under the steps. He had a storage bay, directly behind the front door. He found a battery box that holds two six volt batteries end to end, not side to side. He mounted it against the wall between the bay and steps.

This installation was very clean, took up minimal storage and put the wiring within inches of the other batteries.