Recently, I came across someone asking for some unique help. He was using two different scales in the same mask set: fit to frame for the mask and fill frame for the masked layer. He had two different mask sets that displayed the same image. One mask set was smaller than the other. The information concerning size and position of the smaller mask set were known as was the size and position of the larger mask set’s mask layer. What he wanted to know was how to determine the size and position of the larger mask set’s image layer such that it displayed the smaller mask set’s image exactly the same … just at a larger size.
An explanation (tutorial if you will) of how to figure out how to deal with this little doozy of a problem is located here.