Originally posted by contour_phoenix_when:
I would venture to guess that the result of the cutout diameter being less than the diameter of the 8 inch driver's actual moving cone probably 7.3 inches the waveform coming from the driver will rattle or move the rear deck carpet or board causing vibration like sounds.
I don't know what you mean by that. But, anyway, I believe that Aaron measured the factory hole at ~7" which is about equal to the diameter of the piston on a typical 8". Even if it were slightly smaller, I don't believe that the negative effects would be noticeable.
I still don't believe that any 5.25 or even 6.5" driver is going to give you the bass you are looking for, even if mounted in an enclosure.