I have the Fab Tech shim kit setting's on my '03 450 EXC, set-up to the # 1 stack, which is the softest setting. There is an even softer zero stack, but I havent tried that yet. Moreover, I have both my compression & rebound settings dialed back to full soft as well. And, on top of all that I run Red Line 100% synthetic zero weight oil, just to get that little bit extra plushness. Nonetheless, I still find the WP 48 mm front forks to be too stiff, especially when subjected to side impacts.
Here is a link to Fab Tech :
http://www.fabtech1.net/