In my RV there is an unused cavity just below the kitchen floor but exposed after removing a sheet metal plate in the cab area. The cavity is approximately 8"h x 5"d x 30" w. There is room for one or two 6.5" woofers. Being structural metal, will the cavity work as a sound box? If needed, there is room for a tube port through the floor. Will this cavity work and, if so, what parameters should I consider? Thank you.