I got to the aisle yesterday around 5. There was nothing inspiring, just a few Malibus and Impalas. There was a lone Forte in the Intermediate area and a long row of minivans. So given there was nothing I had my heart set on, I self-identified as a USA one-way to the lot greeter.
He went over to the US cars with me with keys and offered me an Avenger, HHR, or a Traverse. Initially took the HHR for gas mileage, but fearing how my 6 pieces of luggage would fit I switched for the Traverse. Turns out I chose wisely. It had 25k on it, expired XM, and as I later discovered the windshield washer jets had a pressure problem and didn't work. So not the greatest car I've had from National recently, but I was still happy with it.
Car had FL plates and I wasn't questioned about the car by the officer when crossing into Port Huron.
Now the next challenge is managing to get a Canadian-plated minivan for my one-way from Seattle downtown to YVR...