I'm a relative newby to turning and have a problem for which I don't see an
easy solution.

I've just turned a bowl which is 6 1/2" in diameter but with a 4" opening.
The bowl is finished and it is now time to part off the tenon/spigot. My
problem is that my OneWay 4-jaw chuck doesn't open wide enough to hold the
bowl by its opening, and the Jumbo Jaws don't close small enough to hold it
by the opening. The outside from the opening on top to the sides is too
high to be caught by the rubber jaws on the outside.

What is a reasonable solution? Some sort of jam chuck on a spur and hold
the tenon by the tail stock while I part it off?

Thanks.

George (another one)