Change in Encumbrance Type upgrading from R11 to R12 (Significant Loss of Functionality?)

 We're upgrading from R11 to R12. In R11 (and since we implemented purchasing in 1994), we used two encumbrance types, REQUISITION and PURCHASE ORDER, to identify the encumbrance types when the requisition and purchase order were reserved, instead of the seeded COMMITMENT and OBLIGATION.

Now, it appears as thought in R12, you no longer have that choice. Instead of a List of Values for the encumbrance type to be reserved at Requisition or Purchase Order time, there is a simple checkbox.

Is there anyway to change the encumbrance type that is reserved from COMMITMENT and OBLIGATION to REQUISITION and PURCHASE ORDER?