General Port Help

[rpelkey13]

So, I just got done building my box with 2 Pyle PLW12BL's (budget box ftw!) for my xterra, and now realize that 5.26 (not counting the subs) sealed may have been too much. The site I looked on said that 2-3cuft was average for 12's, but I'm thinking now they were wrong. So, now I figure I'll go with a ported design seeing as the size better fits it. So, on to the questions. My bow is 37.5"x17.5"x17.5", and is made from 3/4" osb (not the best, but what was available). I was thinking having it tuned for 20hz, and figured from another site that a 3"x3"x9.4" square port would give me that. Anyone know of a better setup or way to do the port that would help? Btw, this is just for a daily driver, and for sound quality over loudness.