Seriously, to try placements, I tried putting a bazooka in back, in the middle of the car on the seat, and in the front near the dash, and the sound from the front sounds the best, while sitting in the driver's seat. Bass from the back is too boomy!! It has all mid-bass boominess, and no looooow bass! Sounds terrible actually. But with the under-dash placement, I hear all the available frequencies from my JL, and it sounds the best there.
Now if I can only figure out how to compensate for the hard-plastic interior adding to the mid-highs. Anyone tried carpeting the doors to knock down the reflections? ;)