Defining Personnel Subareas

Can we use the same personnel subarea for more than one personnel area within a company code? E.g. Company code = C1; Personnel areas under C1 = PA1,PA2, PA3. Can we define a personnel subarea PSA1, which is under both PA1 and PA2?

Assuming that SAP allows for the above, is it recommended to configure like that? what are the advantages/disadvantages of doing so?

-Shambhvi