LOL....okay, I'm not kiltmaker either, but I am making a kilt. I can hear Barb's voice in my head saying that pleats over 3/4 of an inch aren't quite as pleasing to the eye. That being said, you have indeed laid out one possible pleating pattern that would replicate the sett of your tartan, there is no doubt about that. Well done! There is some "jazz" to pleating the sett, I do believe. IT will never exactly replicate the sett because you are governed by the transitions in the tartan not but the thread count (I hope I am making sense).

So here are the questions you need to wrestle with:
a) Do you wish to keep the exact measurement of the sett (5") and therefore have pleats that are just a little bigger;
b) Do you want to keep the same layout but reduce the width of the pleats to 3/4 which would mean you would need another 7.33 pleats (rough math) TAoK has a method to calculate them out evenly;
c) do you want to split the yellow block into two pleats, which would allow you to keep closer to the original widths of the sett.

I'm sure someone smarter will come along to give guidance. I think using your layout but adding pleats so that they would be narrower would be the preferred option. Don't forget no one will see the apron and the pleats at the same time to be able to notice any difference.