. . . with the lower waistline and if your shirt has a relatively short tail, I think it would look good.
And that was basically my point—it seems the length of the shirt is the key element. Many polos and Ts are short enough to pull it off (no pun intended). Full length dress shirts untucked in a kilt would just look too sloppy for my taste. By the way, I'm with Tobus. My shirts are always tucked when kilted.