help designing slot port box for 2 10" kicker comp vx subs

Hi just wanted some help designing a slot port box for 2 10" kicker comp vx subs, not sure what to tune the port to, the biggest i could go is 38" w X 16" h X 20" d I would like the port in the center and not sure if i need 2 seperate chambers or shared. Im pretty good at building boxs just havent messed with ported boxes much, just want them to sound the best they can, also i listen to lots of heavy rock and metal, if some one could give me some measurements or a design that would be great! thanks