Hiluxmonster, do you have any of the instructions? Sometimes if you call your local 4x4 supplier who deals with tjm regularly they can get a copy of the instructions for a small fee. Failing that, I would take the bumper off anyway because there is a chance you could damage other parts when cutting. Lay the bumper over your wheelie bin, just don’t cut it as well
I fit bars at work but haven’t done many tjm, they all have different methods to achieve the same end result so I couldn’t give you exact guidance.