Taking advantage of time on the lift, I'm working at Pro Automotive for a few days so I don't have to work in the dark on my back under the car. I was happily surprised to find that the exhaust system on the Porsche ran right down the center line of the car, suspended from the torque tube.
A one and a half inch inside diameter piece of outdoor PVC conduit is perfect for getting the cables safely from the front to the back of the car. A couple of two inch muffler clamps secure the conduit to the existing tail pipe mounts. It's recessed into the tunnel and entirely above the level of the floor pans.
The conduit carries four cables. The two orange 1/0 cables are the positive and negative feed from the battery pack. The orange corrugated cable is the charger input from the J1772 charging port (both 120 and 240 volt). I'm using trailer wiring to handle the 12 volt traffic to the AVC2 and emergency contactor. The four 16 gauge wires are color coded and bonded together in a strip that makes it far easier to push through a conduit than individual wires.
There were screws sticking out from the rear seat pan that were very conveniently positioned to attach the cable straps. The cables pass through an existing two inch by four inch opening in the floor. A small plastic filler with two gland nuts will close the space and keep the cables away from any sharp edges.
I also picked up the custom power steering line that mates the Toyota MR2 pump with the Porsche power steering rack. That's another job best done while the car is on the lift, so I'll be back over at Pro Automotive on Monday to install that and finish up the charger wiring.