Do you REALLY have to go through all this crap to mod an N64? Can't you just hold open the cartridge slot and cut/snap the tabs off like you can with an SNES?
You probably can hold the slots open and melt them out, but honestly, the process IGN describes is incredibly simple, I did it for both myself and for UFO and I didn't even look at any pictures before I did it.
edit: The only thing about snapping out is, it won't be as easy as the SNES, as you can see the tabs are solidly mounted at the corners so there isn't really anything you can grip pliers onto the same way you can with SNES tabs. You'd probably have to drill a hole into them to give yourself something grab onto.