better mpg topless?

Am looking at a PT conv. on Saturday... has standard 4 cyl. engine (non-turbo) and auto. It seems mpg really varies a lot depending on driving styles and probably other factors such as terrain, air pressure in tires, etc. I was wondering... do you get better MPG in the convertible with the top down in hot weather or top up and a/c running? Figured a/c would sap some power and make the engine work harder, but top down might create more drag??? Want to know what owners have to say.. thanks!

Not a PT owner but they did do something like this on Mythbusters. They used a Ford Explorer or Expedition. (Can't remember which) They pulled onto a test track and did a couple laps at a certain speed with the windows down. They had a computer hooked up to monitor the fuel consumption. They then took the same car at the same speed with the A/C on. There was almost no difference. The only thing that could hurt you with the top down is if the air gets caught in the cabin somewhere and creates more resistance.