Just purchased a new reflection 337rls. I want to add my current 4-6v agm batts from my last fifth wheel to new trailer. My question is what have other owners done with the factory battery box. My thought was to add 1/4" masonite spacer the size of my larger batt box cut to fit around the factory battery box bottom and place the larger box over it. Or would it be wiser to place the larger box beside the factory box?