You could just have your hatch and rear windows tinted , then no one could see into the boot ( sorry trunk )and you can just take the material cover out.
I've seen so many youtube and "how to" that just say use a wind back tool to retract the rear piston. If you do this with out removing the electronic parking brake motor you are very likely to cause this problem. If you think about it you are trying to force the electronic motor into something...