6th order wall question

[46panel]

Going to be redoing my 4th order into a 6th and am just trying to figure everything out. Using 6 18" IA death penalties on about 2k a piece and planned on having the rear chamber around 27 cubes giving each sub 4.5 cubes. That leaves the front to be about half of that 13 cubes. Does having a larger rear ratio mean it will have a wider bandwidth but not be as efficient as if the front was double the rear. I'm not concerned with numbers but rather a low end daily ground pounder that moves some air.

Also I know the rear port area needs to be quite small and I've heard around 5 square inches of port per cube of airspace. So if my rear chamber is 27 cubes I was thinking like 150" in the rear tuned to 29-30ish hz.