I've never had a problem going through customs when returning from Scotland. Last time over, I took two kilts and three doublets, three sporrans, and all other gear. I did leave a sealskin sporran at home, but took my otter mask sporran. Nothing was ever searched in my presence, and no questions were asked. One time, though, there was a card from the US Customs telling me they had looked in the bag. Must not have been anything to worry them!