Jon, it's www.rcgroups.com Here is a link directly to the thread:
http://www.rcgroups.com/forums/showt...5&pagenumber=1

I ordered some 6mm Depron from www.depronusa.com a few days ago. I'll be starting on the 40" Ultimate for the Hacker B20-15L next week. Should be flying by next weekend. I'll be building another 3DX out of 6mm Depron too. Should be much better than the Fan Fold foam.

Depron is much more rigid, and is about 30% lighter to boot. Until about a month ago, finding Depron in the USA was like looking for hen's teeth. We now have a good source as listed above. It doesn't work out ot be as cheap as the fan fold, but for the guys who can't get fan fold it's great news!

Tim H.