How long are you storing it for? I mean, if it's just over the winter, just fill the tank all the way and start it every couple of weeks. When I store mine, I shift the tranny through the gears, run the heater, run the A/C, hit the brakes, etc, just to get fluids running through it and what not.
When you store a car and the tank is half full, you can get some condensation which can actually form rust, so it's best to leave it full.
HTH
Rich