title_body: What should I use to cover this plane with?
upvoted_answer: How about the thin white polythene/polyethylene from carrier bags or bin liners? I think you could stick it on with a foam-safe contact adhesive such as UHU POR.
  Alternately, you can save weight from your Tiny Trainer by peeling the paper off the foam.
  It sounds like what you really want to build is an old fashioned balsa model, covered in tissue and dope. They're really no harder than the model you have just built, and the balsa for that size of model is only $5-10. The tissue shrinks when you wet it, and then the dope makes it rigid, adding significant strength to the airframe.