my bass question

As my illustration suggests, the port tube can be totally inside or partially outside the enclosure.  You can use available space as you see fit, and the results are limited only by your imagination and the space you have to work with.  The tricky part is figuring out the net volume of the enclosure.  You'll be considering volume of an irregular shape, displacement of driver and bracing, and displacement of the portion of the port tube that is inside the box.

I think it can be don fairly easily with a lot of packing peanuts and patience. So how does this sound.

 First pick a sub, either the MTX of one of the two CVR's, I am leaning towords the Kicker as no one has spoken fondly for the MTX and I know the Kicker already.

Build a box to the specs suggested by WINisd, but slightly oversized,

get the box to the correct post displacemt size with filler

Add port totally external.

is there any thing I need to think about in the design phase about constraint from the port? ie, proximity to walls of trunk, proximity from sub, direction, straight or bent, anything i don't know?

If you build the back and extend the sides out, then you can determine the exact volume needed prior to installing the front of the enclosure. Provided the front is flat and made from MDF. Then you can trim any excess from the sides and fiberglass two pieces together.