I'm not sure I understand the question regarding the proportion of the shirt and the kilt???

As I understand it, a traditional kilt is worn about 2” (or about 2-3 finger widths) above the navel, and that the bottom of the kilt should be between the middle to the top of the knee.

Also, from pictures it is sometimes hard to tell if the kilt is the proper length, as the angle of the photo can be deceiving.