I don't have any experience with Kuiu, but Sitka should fit you.. I wear a 30 inch waist, any my 90% pants in medium are pretty tight fitting around my waist. I'd think you could just about get by with a medium, the small could be a little snug.
Your are correct Fink, my bad. They only go to 32 which would fit a 30 inch waist they seem to run a little small. If they are a little big you can always get a Talus belt and cinch it it up.