It could be, but you could always split the signal from the front rcas into two sets for the front and rear input on your 4 channel amp. This installer is an idiot, the static is from a bad ground somewhere or from something he ****ed up.
sounds like he has no idea what he is doing. I would bail.
doctor for sure.
****ing around with **** like that and trying to be a "man" about it leads to disgusting scars that turn down the baby making music in the future.
you should get a laser jammer, and some veil.
Might run you 350 or so but these things WORK. A detector will only tell you you are about to get a ticket. A Jammer gives you 5-10 seconds of time to slow down before your speed can be recorded.
I would go over to diymobileaudio.com
for SQ and 3 way comp set ups, they are the place to ask these questions, probably already been answered over there.
use the 5s, and just turn them up enough so you can barely hear them for some rear fill.
Rear speakers are an easy way to ruin an other wise good soundstage.