I too have the problem of not a lot of difference between my waist and hips making the trick of keeping the kilt up difficult, not to mention the belt. I wear a belt and use sporran hangers, as a chain really gets under the gut, and the sporran hangers tend to pull down on the belt making the whole thing want to submerge itself below my gut. My solution== suspenders, or braces as they are called in the UK. And yes, I often wear both together. Other solutions that have been mentioned are using a rubberized belt underneath your kilt to act as grippers to both the kilt and the shirt underneath, holding the kilt up as long as your shirt can stand the weight. The same thing can be done with the underside of your belt, and this would help the kilt grippers do their job. I personally have not tried this solution but may in the near future, as my kilt collection enlarges I am not wont to enlarge my suspender collection at the same time.
Good luck with that. And I think you ought to consider joining the social group "Gentlemen of Substance".