Only other trick I know is soak it with some wd40 and then take a torch and run a couple heat/cool cycles to try and get it to break itself loose.I have some heli coil left over from another project. I will have to put my hands on it tomorrow and see what size it is.
Maybe.
I would much rather see about getting it out.
If you zoom in. At the 7 o'clock I might have gotten into the threads a touch.