Not sure really follow what you are trying to do. If you have a front and a back side then you need 2 file outputs from SPA. So you can either 2 batches, one for front and one for back. Or you can make 2 rows in the CSV for each file and have one row for the front composite and one row for the back composite.
Not sure if this answers your question,,,,,,, because to be honest, I was confused by your question.