Trying to remove music from ISO

Hey guys, I'm new to this type of thing and I thought I could ask here for help. I'm trying to remove the in game music from the Persona 3 Portable iso and I'm having trouble getting the iso working.

So far what I've done is, unpack umd0.cpk, convert adx files to wav, silence them using audacity and converting back to adx (I also tried just straight up deleting them, I just didn't know if this would mess up the game or not). Then I used cri to repack the cpk, used UMDgen to delete old umd0.cpk, and insert new file, and then save as iso.

However, when I load the new iso to ppsspp, it doesn't run, and it's just a black screen.

Also for some reason, the iso where I silenced the tracks turns out about 200mb larger than the original, even though the original music files and silenced files are the same size.

I feel like I am missing something, did I do something wrong?
Can someone help me figure out how to get it working?