Is the stuff which you could find in " feather-cardboard " ( french name...Duno if it means something for US modelers ! ), sandwiched between two sheets of paper ?
If it' s what I mean ( a kind of polyurethane extruded foam...the same stuff used by florists to make flowers bouquet construction ! ), I 'll buy some by the ton...!
Listen, guys, if you' re talkin' dioramas of sheer architectural destruction, rows of ( lightweight ) ruined buildings, huge towered " Flak bunkers ", gothic cathedrals....That 's the stuff you ( and I, btw ) need ! (:-)
And you could use it to make trunks' trees ( big ol' oaks, palm trees...The lot ! Although the stronger grade ( hard one ) is better to pattern the bark...), sandbags, paved streets, rocks....
A real fine stuff, indeed...As you could understand, with this enthusiastic speech !