This is using the Version 3.1.5429.42421 of the MET.
In arc, if you tick "Use Printer Paper Size Setting" with in Map Page Size of the Page and Print Setup, then the Page Size field is shown as "Same as printer". I have seen "CU" in this field as well. The validation in the MET needs to pick this up, so that it can be correctly set.
This is using the Version 3.1.5429.42421 of the MET.
In arc, if you tick "Use Printer Paper Size Setting" with in Map Page Size of the Page and Print Setup, then the Page Size field is shown as "Same as printer". I have seen "CU" in this field as well. The validation in the MET needs to pick this up, so that it can be correctly set.