As documented in another thread today, you can wash your kilt hose with shampoo and hang to dry (like I would anyway). You could also get some of those fast dry travel shirts (that can also be washed in the sink). Should be able to bring 3-4 kilts, 3-4 hose, and 3-4 shirts in a carry-on easily. Probably room for an extra pair of shoes. Air the kilts out between wearings, wash the shirts and hose in the hotel sink; presto, 3 wks clothes in a carry-on bag.

I used to take 2 weeks worth of clothes (use the hotel laundry once) in a carry on for international travel back before all these travel friendly clothes came out. Granted I was going to places a lot warmer than Scotland.