Checked under my car and a thick piece of plastic can just go under the spare tire compartment. Not only will there be less wind resistance but it will block all the small pockets where air can get held up.
My spare compartment actually hangs lower than the bumper, so do you think I should still go through this???
Something I didn't think about before. If the majority of driving is city driving there is little need to adjust for aerodynamic drag. Aerodynamic drag is only a factor at highway speeds.
So unless you're on the freeway/interstate on a regular basis, I would recommend not spending the time/money on it.
But then again, I'm the one spending crazy amounts of money trying to squeeze every mpg out of my car, so don't listen to me.