mdf, are you insane? after a few hours lugging that thing around your arm will hurt for days. looks awesome though, but try for several layers of foamcore or the plastic waffle/plastic cardboard, whatever they might call it over there that a lot of yard signage and stuff is made out of. it has the rigidity and look of solid weight when layered and edge covered right, and is still light enough not to pull a muscle.
Sounds like you're gonna have fun lugging that around!! XD;;
awesome job, though ^_^.