I never wear a kilt belt with a backpack - it just doesn't work. I have a fair number of miles, both kilted and unkilted. I also don't wear a sporran, but I have worn a "bum bag" hung in front, for small things like a Swiss Army Knife and Aquamira and my camera (though since my new backpack has pockets in the hip belt I won't need to wear that for my next hike).

You're out in the woods. You certainly don't need to "dress up" a kilt with a fancy belt! No one else is wearing cuff links with their polypro shirts!

Andrew.