Well, I've found that the heavy paper backed foam boards are still too heavy even after you peel the paper from them. They make great template material but forget about it for flying.
Use the blue fan fold foam or Depron or Ultrafoam. Or take advantage of the other designers out there selling kits.
For cheap experimenting, hard to beat the price of the blue FFF. For nicer looking planes, use Depron or Ultrafoam (check depronusa.com or troybuiltmodels.com)