10" subwoofer customer install

[borobrindo]

I've been lucky enough to have acquired a nice pair of Alpine amps and a 10" sub, I often use the full capacity of my boot and don't really want to have to remove a box 2 or 3 times a week. I'm thinking of making a custom enclosure on the side of the boot where the old multi changer was but I'm wondering if it will sound terrible due to the small area behind the cone? Has anyone else done this? My sisters 75 tourer has the HK setup and they put the sub there, btw mine is a MK2 saloon.