Help with ported box for Type Rs
 

I have 2 12” Alpine Type Rs Dual 2ohm and a MRD-1005 to power them. I was hoping for a ported box, but I can’t seem to find the correct dimensions. I am some what limited to space due to my suspension set up, but I am willing to move a few things around. My trunk is 42” wide and 16” high, as for depth, I was hoping for 13”, but if need be I can use some more space. What would be the optimum cubic space needed per type R ported.

The car isn’t SPL, just a fun showish, kind of car.