A PC full Highland dress does really looks like a costume when the others wearing tuxedo. A colourful tartan emphasize this look. In such situations I prefere an black argyle Jacket with waistcoat, kilt in weatherd colours, black kilt hoses with black flashes and a black sporran. This style is not so preeminet and is more accepted than a full dress with plaid. Ok this is germany. I donīt know how it worked in other countries.