Now im back on my feet after poisoning myself its time to sort out my boot build. Is it possible to fit a free air sub into the fire wall behind the rear seat? I know not many people rate free air subs but when set up correctly they can sound very good. What im thinking is to cut a 12 inch hole into firewall, strengthening the wall with rubber matting and sound proof then bolting in the sub so that the sub can use the boot (once sound proofed and sealed) as its enclosure.
I read on a forum in america that its illegal to cut away the rear firewall, is that true here in the uk?

Depending on how high you mount it it may well foul on the back of the seat. Even if it doesn't once installed, then maybe during the low notes as the cone moves in and out. That section of the car is structural, IMO leave it alone.

Have you considered mounting it in the wheel arch recess, there's a link in the Ice FAQ & I'm sure someone on here has done it, using a mixture of MDF and fibreglass to make the back of the box.

I did it (a fibreglasse+MDF front case on the rear whell arch)a few years ago, just have to be careful what sub you choose because there isn't a lot of room for a big box: https://fbcdn-sphotos-a.akamaihd.net/hphotos-ak-ash4/419881_396318117064020_1972348702_n.jpg

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