Well let me ask, do you want to be one of the gents in a gaudy costume? If so by all means wear the fly plaid with the kilt. If however you aspire to look your best and wear something appropriate then I would suggest wearing the full Black Tie Highland outfit. Why not take a look at the 1 Kilt 10 looks thread, that was done a while ago. I think you will agree the black tie outfits pictured are not costumes, they would fit in any Black Tie event.