Give me max dimensions HxWxD and I will try to design you something maybe? In any effect it should either be woofers firing up and port firing back (if its a hatchback station wagon like you say) or do similar to some CRX builds and build a box with 2-4 flare ports off the side of it, both have been the best I've seen for SUV/small hatchback.
Just give me maximum dimensions and requested freq, also I'd recommend anywhere between 38-42 for high scores.