Hi guys, thanks for the info!
I just lost my 180h save (should have made a backup, I know...), and have been trying to HxD my user1 in a new save either to get some stuff to help me get back to G1 rank, or find a way to edit my hunter rank and completed quests.
I tried extracting 'user1' with Save Data Filer, but couldn't get any useful file, the data appear completely different from 2 dumps of the same save. Apparently there's an extra layer of protection.
I did manage to test and successfully change my Hunter's and Palico's name thanks to Banxian tool on MH4U.
I suppose Banxian has found a way to decrypt/encrypt the save.
Liomajor, here's the info you are looking for to fix the guildcards:
http://pastebin.com/CXdd1GaH
However, you will need a way to decrypt/encrypt user1 and card1.
Personally, I'm interested in a save around G1-G3 for me to restart from the point my save got corrupt. If anyone want to share his save with me, I can change your hunter or palico name in return.