I've done that very thing to one tailcoat already, and it's worked out quite nicely. Then I kayaked too much last year and went up a jacket size. There's a uniquely designed Perry Ellis Tailcoat on it's way to me from an outfit on eBay that's about to get the same treatment. "So You're Going To Wear The Kilt" has a short guide on how to perform the alterations. It's really not that difficult, lads. Although it helps to have a mother with 65 years worth of sewing experience around for assistance as well!