I too have been messing with the GH DLC a bit. Here is what I've found so far, maybe save you some time:
DLC uses a new content type. In the past, there was only 0x0001 (local APPs) and 0x8001 (shared APPs). With DLC (not just GH, I've seen it pop up in MM9 and Samba De Amigo), there is now a...