good. I can't remember a 6k file where I changed root bass sound, but I have sequences and setups where I deliberately saved those volumes at zero on 6k, and they still load OK on the 7k. There could be several explanations but I would need a file to see exactly.

You don't need a great deal of space behind the port as long as you don't block it. Subwoofers sit only a couple of centimeters above the floor and deep bass wavelengths still propagate fine.