This is an FYI for anyone who does not get American Woodturning and is
thinking of getting Coles jaws to hold bowls or looking for perhaps a
better way to finish the bottoms of your bowls so I'm not expecting
any replies.

The Spring 2008 American Woodturner (you can order a copy from the
American Association of Woodturners web site if you are not a member)
has an interesting article on the Straka chuck. It is used for
reverse chucking. I wish this article had appeared a few years back.
Rather than buy a second chuck and jaws to hold bowls up to 8", I
would have made one of these chucks instead and been able to hold
bowls up to 12" (I have a 15" lathe). It is also a cheaper way to
go.

The chuck has a faceplate connected to two plywood disks (glued
together) potentially as big as your lathe can hold. Next, it has a
plywood ring held by bolts to the first disks. Finally there is a bowl
sandwiched in between the disks and the ring if you can picture all
that. The article has pretty good directions on how to make the
chuck.