With that large of a tartan, I was left to either makes pleats that were huge, or come-up with another solution. The solution was to alternate specific lines in threes. Since the pattern is such a broad, but symmetrical pattern, you would start with one line... go in about 7 for the boundary... then another 7" for the next boundary. If you reverse the pattern for the next three pleats, then you have the pleating. I was actually impressed how well it worked, plus it kept the symmetry. I wish I had pictures of the finished product!

If you have the time to pin it up, you'll see what I mean. Question? PM and we'll work it out for you. Once you have the idea of the pleating down, it's really quite simple to do.