You know, since Grace is technically a cyborg/android, her three sizes technically still fall under this thread.
Also Meltran cup sizes would probably have to use an upscaled version of the current size system, where the difference between underband size and overbust size in cm or inches would be multiplied by a certain amount (how much bigger is a meltran compared to a micron female again). In other words, in terms of proportion, Klan is probably around DDD meltran (6 inches difference between underband and overbust multiplied by how much bigger a meltran is compared to a micron female).
To put it into mathematical terms:
meltran cup size=(x-y)/z
Where x is the overbust size, y is the underbust size and z is how much many times bigger a meltran is compared to a micron female. Then compare the resulting figure with the modern day cup size chart.