Sub and Port on same side?

IMO. Even with them facing opposite sides. With say the port facing forward, the sound from the woofer is still radiating from where the woofer resides (can't post images to help). Therefore the sound waves from the front and back are not that far apart. I would imagine that if the woofer is then a couple of feet from the rear of the vehicle, that could possibly then radiate sound waves that would end up causing significant cancellation. That's why you want to keep the port and the woofer (same as all woofers in a multiple woofer setup) within 36" of each other. Closer would be better. Mind you...I have some real world, some formal electronics training, and LOTS of reading on this forum and other sites. But I do not have the expertise to back this up scientifically. With some of the posts that I've seen between DYohn and haemphyst, they would probably be better on the scientific end of it.

I DO know that you want them as close as possible to avoid as much cancellation as possible...but top and front or side to side shouldn't matter too much if they are close enough and directed to the listening area through the same general path. In other words, you don't want to have the woofer pointing through the seats and the port having to go completely around the box and up through the rear deck adding another 3' to 4' of effective distance before the sound waves meet.