[Formerly Steve Wilkinson]

Depending on the configuration of your pump--how long a nozzle it has--it really doesn't make a great deal of difference how high you raise the car, as long as you have adequate access to the fill hole. I've always just used gravity and a length of Neoprene hose so am working from the area of the left rear wheelwell and haven't needed much clearance under the car. (A pump does sound like a better idea, since the gravity-fill method takes awhile.) If you need to get in there under the thing to work a pump, you're obviously going to need more clearance, but that's the only factor determining how high to raise it. Me, I'd put a flexible extension on the pump (if necessary) and work alongside the car rather than under it.

Stephan