i2ain2thunder 10+ year member
CarAudio.com Veteran
also add bullet proof glass and flame throwers!You should get some lead sheeting and also mount it to the roof, i filled part of my trunk with concrete to help lower the resonant frequency and it made a MAJOR difference in the low low notes. Adding mass to the floppy parts of a vehicle is always gonna lower the resonant frequency of the car, and help stop flex. Add some more weight to the roof while youre under there.