Try "FitCaptain01_en." That's what the filename for Falcon's red costume is on the disc.

Thanks, I will try that! I was following a page that said the name was "FitCaptain01us", so it was probably mistaken.

Edit: It worked! Thanks for the help!

Edit 2: Also, I just noticed this while playing:
http://puu.sh/9SCxh/f65cc8136e.jpg

Hey bro, I'm loving your melee hacks and everything. Just a question though, I'm trying to get the Blood Falcon skin of Melee Falcon working in Project M, and it just doesn't shows up. Renaming them to FitCaptain01us doesn't work, either (I'm using a NTSC Brawl iso). Can you help me in any way?

Hey man, dunno why, but your Snake from Ground Zeroes doesn't work in my game, crashes it from the character select screen (have him over Panther Skin Snake, when I select him, game crashes).