Thank you for taking the time to post this thread! I know it will be appreciated by many members who are looking to do the same installation.
I have 2 quick questions for you:
1. Is your subwoofer enclosure fiberglass, or some other material?
2. Do you have any overheating issues with the amp installed in the hidden compartment under the carpet? I was hoping to do the same (in an e90, which I think has a different shaped compartment from your pictures) but was a little concerned about heat - there seems to be no ventilation.
Any info you have on those questions would be appreciated. Thanks again!