@tilton There's a definite art to these things, penetrating oil is one of them, be very careful. Sometimes, tightening them slightly first can work oil in a bit deeper, but don't go far. If you get one moving a bit still tread slowly, applying heat, oil, working it back and forth. Sometimes even imperceptibly back and forth.

As a victim of snapped fasteners, they always happen when I don't got slow.

It's better that it takes a week to get a single stud out than to snap it, put a bolt extractor in there, and snap that and then have hardened steel in the stud :P