That was designed for two 10s and it's 3.5 @33hz. That's about 1.75 per sub so it's a little more than what you said but I already had the design finished so you can use it if you want.
thats my bad i meant 1.3 cubes per sub so arounb 2.6 its going in the back of a civic so if you know how big that is because i dont have a tape to measure it at the time but thx for the repplys