I started this topic in a separate thread, but felt I wanted to include the information in my build thread as well. I installed the charging port today. It's in the trunk floor near the latch bar. Pretty simple to do except for one little gotcha that made me have to do a bit of extra work. The polarity was reversed (port wired backwards). Thankfully, my charger identified the issue and I was able to correct it. When I tested the port, sure enough I was getting -0.55 on the multimeter with the red and black wires tested as indicated. Reversing the two proceed a 0.55 reading. So, after reversing the wiring, all was good.
I used stainless hardware instead of the stuff that came with the port. I also swapped out the 30 amp fuse on the holder with a 7.5 amp fuse to match what Optima uses in its accessories.