Sending Subledger Txns Sent to Different Ledger via SLA Application Accounting Definitions

From what I have read I believe it is possible to create GL entries in a ledger different than that of the ledger tied to the OU and BSV's with Application Accounting Definitions in SLA via copying seeded definitions and changing them.  But I am missing the connection between the SLA and the targeted ledger.
The diagram shows two operating units with one OU1 generating journals in both ledger A and ledger B.

                    Ledger A     Ledger B
                          |            /      |
                          |           /       |
                          |          /        |
                          |        /          |
                         OU1             OU2


Anyone have any insight or a good white paper on how to get SLA to generate journals in different ledgers?

Thank you