So I'm having a little trouble with the math here. If you have 13 oz tartan with a 9" sett, why are you only getting 15 pleats if you are doing one pleat per sett (rather than 1 pleat per half sett)?? Do you have less than 8 yard, or are you making a kilt for a larger person (e.g., hips a lot more than 45")? If you have 8 yards of tartan and you're making a typical knife-pleated kilt, you'll put about 6 yards into the pleats. 6 yards at 9" per sett would give 24 pleats if pleated to the stripe, or about 21 pleated to the sett (pleating to the sett gives 2-4 fewer pleats than pleating to the stripe). So I'm not sure where the 15 pleats come from.