[Tricky Mike]

I once pounded a Torx driver into an appropriately sized hole... It's hardened steel, so the bolt should deform around it and give it a decent purchase. I was surprised how much torque I was able to apply... May be one of your options to try befor the last resort... Have you also heated the case? Used some penetrant? Those damn screen bolts freak me out every time. They always take tons of torque.