I recently rediscovered an early kilt I made, in just that tartan, and I made a mistake in the measurements, resulting in the length of pleats being too short.

As I had the apron and most of the pleats done, I simply took another piece of the material and joined it on - it is not very obvious and anyway it is just about hidden by the outer edge of the apron.
Problem solved.
I made a couple more pleats and the under apron pleat from what would have been the under apron - and now that I have lost a bit of weight I can probably remove a pleat and shuffle the join even further out of sight.

The term 50 yard kilt is definitely one to savour.

Anne the Pleater