the sub panel has not been reinforced; I was thinking about doing it, but I tried without and thought it was pretty solid already.
I'll post some more pics of the sub panel and also the GND connector for the amp.
A couple more info....
If you want to install the same amp or another one with same dimension, be advised thet since there is a bunp in the middle of the "hole" under the trunk and there are 3 screws.... installation become difficult, I isolated the top of the screws and installed the amp without the bottom panel so the screws have some space inside the amp.... careful to check the screws will not run into any part.
If you want to install a different sub search a sub that:... first the sub has to be designed to be installed in a small enclosure (strive for a recommended .75 cu. ft. sealed or less) and second make sure the mounting frame and magnet dimension allows the installation 'cause the shape of the plastic in the back of the panel does not allow a big one...... By the way the sub is a 10' sub