I took the displacement form both woofers and ports, but I builded the box at 2.4 feet so its 0.35 off, would that drop db's are hurt the woofers, but the box sounds good.
it want hurt the subs n anyway if its bigger it will drop alil bit lower mayb a db and the oppsite if smaller and if its just .35 off then u could make a ring 2 go under both subs and that will get alil back for you so u dont have to build another 1 but thats only if the box is to small if its to big just add some bracing on the inside to make up the extra air space