Well here I come from the other side. I like wearing a full plaid! (Glad you droped the term "Piper") However, when you go to buy one, you will probably find it listed as a "Piper Plaid". You can buy Tartan matching plaids in the same fabric as the kilts from SWK and Frugal Corner. These tend to be smaller than the traditional size but still work to wear in a belted style. I wear this with my kilt whenever the weather allows. Though I have not worn one with a jacket, I have seen enough vintage pics to know that plaids were worn with day wear jackets. (Though not in a belted style.)

To me, if your going all decked out in "modern" formal kilt attire, then I would wear the "modern" fly plaid.