Paper Cardstock has some very interesting properties that allow it to be used for model designing. It has been used for years in the model aviation market! http://www.jetex.org/archive/article-rigby-pw.html link showing designs for the old jet-x engines. -Cheap -Glue doesn't try to kill/stone you! -Very forgiving during construction-easiest medium to get model to fly (afterall it is paper-just add a tab to a wing to correct for wing drop or for yaw problems do the same to the rudder) -No jigs needed! -durable (foam fails to fly after a nose-in, so does balsa-cardstock can usually be "pulled" straight for a couple of more flights) -easy to scale up or down -excellent color schemes (not much weight added) -model is done in less than a weekend in most cases (18-hours on 6.5 long SR71) The downside: -Humidity!! Weight and balance changes with the Humidity! Don't even try to fly when it is above 90% Humidity! Photo show how easy it is to mount the Rapier engine in the wrong place! Balance weight would overcome the engines thrust! Engine like Jetx must be mounted near the CG! Lesson learned after doing it the wrong way!!!