i didnt do it, but the PO did on one of my jeeps. it was a good addition to the rear sound bar, but i personally dont think it could be a replacement. the location of the sound bar allows the audio to go forward through the cabin while the rear speakers were almost muffled down there, especially when there were people sitting in the back
the problem with the ones i had was that the plastic trim pieces of the speakers protruded out and werent flush with the door. so every time people would get out of the back, they would kick them. im not sure if this was just due to poor installation, certain speaker style, or lack of room. but what i had to end up doing was taking some heavy duty wire mesh covers from other speakers of the same size and putting them over the speakers instead of the usual plastic trim
i played around with the front/rear fader of the speakers and lowered the fader in the rear to get rid of that "in the ear" problem. the custom rear speakers were wired in such a way that they were affected by the front fader, so it worked out great.
i never messed around with the speaker wiring so i cant give you any pointers on it. all i know was that the PO was an electrical engineer for the navy or something and that it was done right