When I rent a car, I want the smallest most compact vehicle available. I drive alone, I'm short, I want the gas savings, and don't want to worry about fitting into small parking spots.

I sometimes get upgraded to larger vehicles, which is the opposite of what I want.

What's the best way of contacting a rental outlet to communicate my preference? Is there a way to indicate my preference in my Hertz Gold Account? Or do I just have to call/email every time I rent?