jeff'
my Hornady titanium-nitrided dies for the .44 mag' will handle the .445'....from what i've measured. take off the depth of the .445 brass in the shellholder and add up the 1.63 inches inside the die and you should be able to handle the supermag'. the dies are not labelled for the supermag', however.
i would not back off the die from the shellholder any more than is absolutely necessary. you want the round to chamber easily and that can become somewhat difficult if you partially size the brass. at least, that's a problem i once ran into with a tightly-chamber Ruger revolver.
good luck,
ss'