clutch nut removal

[Gary H]

Comrades,

I've been having a heck of a time trying to get the clutch nut off of my 75 GL1000.

Engine is out.
I've tried heat, impact and penetrating oil. Used a screwdriver but also I have a clutch tool and the correct clutch nut socket.
Nut restraining tabs are out of the way.

Does not want to budge.

Any advice or techniques?

Thanks a bunch for any clues!