I was just crunching some rough numbers and a ported enclosure for a RSS390HF, at about 10 ft^3, would measure approximately 36" x 24" x 20" and will probably weigh about 120lbs, or more.
I'm having 2nd thoughts about that driver now. Although there is sufficient space behind the false wall to place a pair of these, I won't have any room to get behind to do anything else, like putting up bass traps, for example, or accessing the back of my components. I won't have as much lateral leeway in sub placement as well.
Plus, although I would get assistance to get them behind the wall, it'll be awfully awkward. To top it all off, I have a very small shop. So small, that I'm concerned about assembling and moving such behemoths around.
I'm wondering now, if the Epic might be the better option after all.