Here are the neccessary files:
http://pastebin.com/N0jZ8xRE - the class that is registering the turtle upgrades, yes it is called, I debugged it (crashes at line 21 because of debugging, NullPointerException), because the turtle upgrade is not registered (without line 21 of course it runs but when I try to craft upgraded turtle/equip item it does nothing/ says item is not equippable)
http://pastebin.com/QRKEHNhM - the ITurtleUpgrade, the debug at line 28 is successfully output to the console.
Edit: solved, it seems that the integer id was not enough, a resourcelocation id was neccessary too
Edited by Konlab, 23 March 2016 - 02:06 PM.