You can cut in outside the cup, the reason I cut it inside the cup is because the strain relief was hard for me to get out of the cup. I didn't want to pull the strain relief and risk pulling the wires that are connected to the driver off the solder pads, so that's why I did that.
Thanks so much for the method. :D I'll be looking to order the equipment today. Also i'd like to ask about the part where you cut the cable. So im cutting the cable from the inside, not the outside of the headphone? Because i read somewhere earlier in the post it was the outside of the headphone. Just wanna double check. Thanks :)