I am assuming you mean a traditional 4 yard box pleated kilt here. My advice applies to all 4 yard kilts, regardless of how they are pleated. I only make box pleated kilts in medium weight (13 oz) wool or heavier. I actually prefer 16 oz, but will use the 13 oz if that is all that is available. Anything lighter just doesn't do as well in a 4 yard kilt.

In an 8 yard kilt, you have the additional depth of the pleat, as well as the sheer amount of fabric, that makes the lighter weights work better. But not so in a 4 yarder.

Matt