Since the top of your kilt rides higher than your everyday jeans by several inches you will naturally feel a pull in at the navel level when bending or sitting, some of which may be improved with proper fitting of a bespoke kilt. Also, since your belt rides higher as well it may be causing some of that pressure.

If you do a good job sweeping your pleats when you sit down the pleat rise in the back should be minimal, and I can usually keep my pleast down near my lower thighs. But if you have a large derriere' (ask robert to translate if necessary) you may end up iwth an overhang scenario which could cause greater posterior coverage issues ( actually less coverage)when sitting.

Best advice is get used to sweeping your pleats fully while bending 45 degrees forward when first sitting, then pushing down your front apron center while dropping to your seat and using your sporran to help keep your aprons down. Avoid low cushy couches at all cost. Crossing your legs can be problematic unless well practiced---instead keep your neeks a few inches apart. Never attempt the cowboy leg cross----one ankle up on the opposite knee without lots of experimentation or experience---very challenging maneuver, and I doubt one that is seen often in the highlands. Always be consious of pushing down your appron front until it becomes second nature.

j