Hi,
Here is an idea I saw somewhere on the Web, I can't say exactly from whom it is.
It is a set of soft jaws to be installed on a heavy duty vise for holding delicate wood and non parallel pieces :
http://www.labellenote.fr/file/Luthe..._mordaches.jpg
http://www.labellenote.fr/file/Luthe...ecartement.jpg
http://www.labellenote.fr/file/Luthe...che_courbe.jpg
http://www.labellenote.fr/file/Luthe...che_droite.jpg
I have an article on my site for that :
La Belle Note - Soft vise jaws for the luthier