Final install.
I have to reach a tiny bit to press the switch. I considered foot pedals, but installing one of those would have meant drilling into the floor, and I just didn't want to do that. The black switch on the column is EFAS, the little silver switch on the wheel is my brake (full-regen) switch.
I used the wrong kind of switch for EFAS. It works, but the correct switch would be an SPDT maintain switch. This one has a third neutral position which shouldn't be used. In the photo it is in normal driving mode, when I push it in to the I position at the top it switches the signal to the ECM to come from the Arduino, and then the car goes into Auto Stop if in neutral. Sometimes I have to tap the brake switch to get AS to happen, but that's no biggie. When I want to drive again I press the switch back down to the II position and then I shift into gear. In a pinch you can just shift into gear and the engine will restart, but if you leave the switch depressed in the upper I position you won't get assist or regen.
I'm really happy this project is completed, and I'd love to help anyone who wants to build it for their own car, so just ask if you have questions.