I've not begun my own kilt, but when I was working on the splits I measured the splits of the 8yd wool and the casual kilt I already have. The aprons are not the same, yet both kilts appear fine on me. It basically comes down to how much of an "A" of the apron my frame will accept.
Along with Adrian's advice: From your comments it seems you have a kilt already and we will presume it looks smashing on you- so perhaps you might decide what you think is best from your own measuring process and then measure the kilt you have as a "test" of your decision?