Flywheel nut removal

[David Stepney]

But the Porsche doesn't have a 90 year old aluminium crankcase with a very flimsy top corner of the flywheel housing unsupported by the gearbox and having a hole to weaken it . 

I would be very careful

True, Tony, but the Porsche engine is also made of aluminium.

I agree that one should be very careful, especially when applying large amounts of force to any component, The law of unintended consequences can be quite devastating! Perhaps in the instant case, it might be safer to drill the nut, split it off with a sharp chisel and fit an new nut.