Lost Weight....Now What to do??

[The Wizard of BC]

To keep the kilt symmetrical front and rear both right and left buckles need to be moved equi-distant. The problem arises due to the opening in the kilt for the right(Left) strap to go through.
That hole determines the position of the right(Left) buckle and its tab.
As a quick fix you can move the Left(Right) Buckle Tab rearward. Then detach the Right(Left) strap from the under apron and re-position it forward onto the front of the apron.
Not a problem for a size adjustment of only 2" but if you try this for adjustments of greater than that a kiltmaker will need to re-position the strap hole.
This entails unstitching the liner, opening and re-enforcing a new hole in the pleats, then closing up the old one and re-attaching the liner.

If your adjustment approaches 4", and you don't re-position the strap hole, the kilt, when worn with the front apron centered, will show the back off center.
Some kilts can be worn with the back off center and you will never know it but if you have sporran loops, the kilt is pleated to the Sett, or on a box pleated kilt, the off centeredness shows up from 30 ft. away.