I have had it done with a non-Barbour wax coat. No problems at all, just took it to my tailer (cost around 90 USD). Negating the waxproofing sounds a bit strange. I would not do it with a gore-tex shell jacket but this is just cotton and wax. I lengthened the sleeves of my Beaufort with Barbour, no problems there either (pretty expensive though, for an easy alteration).
10/2/10 at 5:56pm