The offset can be calculated... and that offset may not be correct for every type, it really depends on the header information
Above you'll find a snippet of code from my tool that reads the information
SOLVED!!!
The DLCs was for NTSC zone and my game was PAL. I replaced my PAL game by a NTSC version and all 4 DLCs is working now.
Very happy because I started to become nuts
Thanks for your help Swizzy.