the trunk needs those bars. I've considered removing them for sub clearence, but looking at how they work, they're pretty nessisary.

you could try a custom install into the rear door panels. But I assume they're 6x9s, so that might be too big.

if you do mount them on the top of the rear deck plastic, put some foam or sponge material between the metal and the plastic to create support, then it shouldn't vibrate bad.