cam cover bolt rounded

[Chimp871]

Starting to remove the cam cover and one of the bolts rounded on me.

I'm planning to heat the area, use gas plus, drill the hole a little to clean the edges and then tap in a suitable male torx bit before trying to unscrew.

Before I do so, just wondered if anyone had come across this problem and found a more gentle approach?

[TwinKam]

No need to drill first, just tap in a Torx or a Spline bit, it'll broach its own path, and the tapping will help by shocking the thread too.