FYI: all the flite test plane kits are made from Readi-Board, the stuff you get from Dollar Tree. I build almost exclusivly with the stuff and it can handle a lot of abuse if you have a good build technique.
Depron is hard to find in the states. There is a foam board sold at K-mart and office max called "EcoBrites" made by "Royal". It feels a lot like Depron but cant confirm it is. One thing about Depron is that it can easily crack from impacts. It cant take hits as easily.
Readi-Board is XPS, Extruded Polystyrene. Its flxable, but with nothing more then packing tape you can make it stiffer.
Both materials come covered in kraft paper. A lot of poeple remove the paper since it falls off very easily if it gets wet. Where I live there is enough moisture in the air alone that it weakens the bond and I can easily peel the paper right off in a single sheet in seconds.
(yes, thats me, being lazy on a sunday morning)
Here is a thread (though on another forum) dedicated to planes made from Readi-Board
http://www.rcgroups.com/forums/showthread.php?t=1020909
