Hi Hector
If there is a field in HeaderPed with a matching value to a field in DetailsPed, then you can use XSLT to deepened the XML. More details in my article below.
XSLT approach to enable FCC for deep structures (Part 2 - Flat File to Deep XML)
Alternatively, you can opt for a custom adapter module that I have developed specifically to tackle FCC for deep structures. Check it out below:-
Rgds
Eng Swee