I just put a sub in my trunk. I plan to create a cheap pass through (2 actually), but essentially cutting two holes in the rear deck (where the 6x9s are mounted under the rear window) and then 'framing them' with some sort of plastic piece so that the holes look good.

Each of them can only be a few inches by a few inches, but I have some room to mess around with the actual size and shape of the hole.

In my head, I visualize something that will look kinda like a plastic electrical outlet, except cutout or 'grating'.

Anyway, does anyone know where I could find something like that? Or is there a much better idea out there?