Hey, sorry I couldn't help out. I just got muddled up between 3ds to cia conversion to extract and edit the romfs (which I remembered wasn't possible with cias), and a program which can run patches on the .3ds file to get the rom hacks onto the rom.
@Xdqwerty, Osu! Tatakae! Ouendan! is the Japanese version of the game, different settings/characters/songs but otherwise identical mechanics. I played that before I knew about Elite Beat Agents lol. Both fantastic games https://en.wikipedia.org/wiki/Osu!_Tatakae!_Ouendan