George Leeman, who at one time recently was the US record holder in deadlift recommends a higher belt position. He has a belly.
Here's a video from him on the subject:
My Opinion on Belt Position for a Huge Deadlift! - YouTube
I have always worn a belt pretty low, around my navel/hips. LAtely, however, for back squats, ive been wearing it higher, like George. Althopugh it takes a workout or two to get used to it, I feel it gives better support for squats and deads. For Bench and press, however, im still wearing around my navel. Wearing around the navel supports my guts better, wearing high supports the back better.