Andres,
I'm glad we could help you.

Masking tape is great for keeping pleat edges out of the way while sewing, but I only use it on the inside and use pins on the outside.

After lots of trial and error I've concluded that the "big pleat" shouldn't be more than about 3 inches deep.

If you are putting a waist band on your kilt, it should certainly cover the entire top edge of the kilt, including both aprons.