Caliper Guide pin

So, I'm stuck on one of my caliper guide pins. I've got the kind with the 7MM allen head.
Of course I've rounded it out applying too much torque.
I've cut the rubber surround off of it so I can get at the shank part of the pin. It's too smooth to get a good grip with the vise grips.
I was contemplating taking the grinder to it and grinding two flat spots on it so I can get a better grip. Has anyone done this, and does anyone have any other suggestions?
I should note that this is part of an axle swap, so the knuckle is sacrificial at this point. I'm really only interested in saving the caliper, and of course I need it off so I can swap the rotor and bearing hub to the new axle.

I would grind it flat on both sides like you suggested. Use a wrench that fits, or a cresent wrench to finish getting it out. Just buy a new bolt when done.

mine rounded out too...I used a small pipe wrench on it...came right out.

just for those that search in the future.
I ground two flat spots on it, then used some straight jaw visegrips to get it undone.
Once I broke the torque it came out fine.