Umm I'm having a bit of a problem. I need someone to go into bass box pro or whatever you like and design me a box. The external dimensions are 27Hx40Wx25D. I'd like it ported. Please don't tell me to get different subs or a different car, I just can't make that happen.

You are definitely small for a pair of SSD18s, but still doable. Im hoping that you have the copper coils as it will help some with the smaller space. You have 13.35 cuft to work with... so honestly this is going to be a tough one to fit. Trying to keep things around 12 cuft total really limits port sizing. You will absolutely have to radius all port edges to keep noise down.

For port forward you could do 4" X 25.5" X 16" long or with port up you could do 4.5" X 23.5" X 17.5" long.

Aeroports are another option you coild try as well. Approx (6) 4" aeroports ((3) per side) that are about 17" long in the center section would work well.

Are you sure that's going to be enough port area? That's less area than I have for my box right now. And btw I would sand down the port anyway, I always do. Thanx greatly for the input.

What if the subs were forward, and port was forward below the subs. Having a 21" by 6" port will yield 126 square inches of port area. I know by rights that's not enough, but for a real world application, will this work?