Trying to get Payment Predictor to work when Customer does not provide Item ID/Invoice ID

We have recently looked into the possibilities of using Payment Load in combination with Payment Predictor.

The scenario is as follows:

Our AR item is a at the Invoice sumaary level, so 1 item per Invoice.

We will receive a payment advice that we will load into AR which creates the deposit. This includes the the following information:

AR_PAYMENT_EC: DEPOSIT_BU, PAYMENT_ID, PAYMENT_AMT, ACCOUNTING_DT, PAYMENT_CURRENCY, BANK_ACCOUNT_NUM, BNK_ID_NBR, STTLMNT_DT_EST, EDI_TRACE_NBR, DATA_SOURCE (CRX and 820), MATCH (Y Payment + Remittance)

AR_IDCUST_EC: BUSINESS_UNIT, CUST_ID

AR_IDITEM_EC: PAY_AMT, BUSINESS_UNIT, REF_QUALIFIER_CODE (P for PO reference, so we don't receive our Invoice/Item ID), REF_VALUE, PAYMENT_CURRENCY