I’m installing a winch on my 2016 P1K5 and will power it with a 2nd battery. I have also installed a True Dual Battery Isolator but don’t really know where to ground it....can I run it to a frame rail and ground it? Or can I run it to the main battery negative post? I do not have the pre wired ground like the 2017 and up models. I am a novice at this so any tips would help. Thanks