F110 - Pmnt adv - can specify bespoke SAPscript but not bespoke print prog

Folks,

As developer I have a requirement to develop bespoke SAPscript to print off payment advices via F110.

I have taken a copy of standard sapscript F110_IN_AVIS to create the Z version, and know how to specify this bespoke form via transaction FBZP>Paying company codes>Forms.

I can also see where you can specify your own form via config of variant against program RFFOAVIS_FPAYM within F110.

But nowhere can I find how to change the print program from RFFOAVIS_FPAYM. I need to change the print program, as the new bespoke SAPscript will incorporate additional windows for company logos and extra texts.

Does anyone know how/where I can specifiy my own print program, is it possible?

Much appreciated and many thanks in advance.

Jon-Paul.