And in many ways, moving the buckles is a better solution than rebuilding the kilt that much. A kilt alteration will change the size of the apron and underapron, but not the pleats, and removing 5" on each side of the apron would make the pleats come around the front of the kilt way too far. The only other choice is to completely rebuild the kilt and take out pleats. If you have someone who can do a competent job for free, this is an option. But most kiltmakers would (or should!) charge nearly as much for such an alteration as they would for the labor of making a brand new kilt. I would move the buckles for now, and, if you maintain the weight loss, sell the kilt and get a new one made.