Classic scenario CUF to R3

I've been reading about Extended Classic Scenario (ECS) and how to get customer fields (CUF) to R3 using a BADI. Is something possible for the classic scenario also?

I've defined CUF in INCL_EEW_PD_ITEM_CSF* and they show up, but I want to map the CUF to R3 fields.

Maybe it's just a matter of defining the ZFields in the appropriate append-structure??

Regards, Léon Hoeneveld