Have ya tried flipping your irocs around backwards? You would be making the outer lugs into more of a grabbing edge for the hard frozen stuff, and the softer snow might get pulled to the center to help you stay on top.
I don't have experiance with snow but in the soft sand my irocs work best in the standard direction, as they will dig , and pull. With them turned around backwards I loose out on the really soft stuff couse all the soft sand gets pulled to the center of the tire. It just might work in snow though as snow tends to stick to itself.
