Customer downpayments

Hello all,

We use customer down payment process where our down payments are booked with transaction code F-28(incoming payment) instead of F-29 and also we use F-32(customer clearing) for clearing the down payment against the customer invoice. This clearing books with document type SU. Now if we want to track down the customer down payments by just using the document type in our custom reports, it is becoming difficult because SU document type is used for other business transactions too. We know that SAP standard customer down payment process includes F-39 for clearing the down payments which books with document type DA.

F-28(customer down payment): Cr. Customer (19A)
Dr. Bank clearing (40)

F-32(Customer down payment clearing): Dr. Customer (Customer advances Recon.) 09A
Cr. Customer (Customer AR Recon.) 17

What is the best way of booking/clearing customer down payments and tracking them?

All your valuable suggestions are most appreciated. Thanks!