1. Install AC3
2. Make a backup of your AC3SP.exe
3. Install Benedict Arnold DLC
4. Return your backup of your AC3SP.exe in the main game folder
5. Go to "C:\Users\Your_User\AppData\Roaming\Theta\orbit\54"
6. Look which one of your 1.save 1.save.metadata or 2.save 2.save.metadata files inside have size 3KB(2KB) and 1KB
6.1. If 3KB(2KB) file is 1.save  copy everything from "54" folder and replace with yours
6.2. If 3KB(2KB) file is 2.save delete it then rename the file from this unlocker to 2.save and paste it.

Unlocks:
Benedict Arnold DLC
Lost Mayans Ruins Mission
New colours for the Aquila
Upgraded Naval Convoy
Scotish Flintlock
Boarding Axe
Pirate Flintlock
Obawandiyag's War Club
Traditional Colonial Assassin Outfit
Ezio's Outfit
Captain of the Aquilla's Uniform
"Sinking a Secret" privateer contract
"Ghost War" privateer contracts


Credits:
IamAWESOME - for providing dlc saves from original game
Brucie - for encrypting dlc's to work with any save made with THETA crack
JorjVirus69 - for giving the idea for decryption/encryption