Are you trying to downgrade manually by making your own .ipcc file?
Yes, I do downgrade my carrier version when they force the update on me. What i do is add the repo
http://v.backspace.jp/repo and I install and uninstall Carrier Update Remover to bring me down to the generic carrier 14.0
It would be nice if you could tell me how you're manually doing because it's nice to learn the manual method
Anyways, I'll upload the file in around 30 minutes when I have access to my computer
Edit: is it the carrier.plist inside the unknown.bundle?
edit: here's the carrier.plist file from the unknown.bundle if that's what you're asking for. The file structure is a bit different from your normal carrier package when you use the default carrier 14.0
https://www.dropbox.com/s/kozwxshe1ayx6ps/carrier.plist