Sorry for not being very clear, let's see if this helps.
1 thickness layer all the way around the waist with a second layer added at the location of the holster (extending past the holster a few inches). NoahL you may be correct with it still sagging but I wear jeans with the belt loops rather close together and sagging hasn't been an issue with a single layer belt. What I'm trying to prevent is the holster top rolling outward. With a single layer belt I find myself cranking my belt tight to hold the top of the gun in close to me. When I have worn a double layer belt I wear it a lot looser and the top of the gun stays in close. I'm in need of a new belt and was just thinking of different ideas of making a belt stiff without having the bulk and stiffness all the way around me, just at the holster location.