Ok im designing a ported box for 2 12' Alpine SWR-1242D's and I was wanting to know if you have to enter the system input power to get the box's port tuning right?

Also, does it matter if I have a little section of box that the air has to squeeze through before it gets to the port? Here is a pic of what im talkin about.

http://putfile.com/pic.php?pic=6/17300474992.jpg&s=x4

Its the box im building on a CAD program for my truck.

Thanks,
Nick