Marty: If you like the NutBall and want to crank it up a notch, you'll love the Drenalyn. They're both loads of fun, but different to fly. The Drenalyn is 'yank n' bank' and will do more. It's a real good inverted flying machine, even at a crawl and I've seen guys cut their inverted flying teeth on them.
ChrisE: Yes on the line and the CF is inserted into the foam on it's edge into a slot. Using EPP you need something to prevent the fuse from bending to hold the airfoil shape. I've build them from 6mm Depron and seen other in FFF, and the stiffener is not required. If using Depron, keep in mind that it bends one way better than the other. If FFF or PB111 is used, place the ripple span wise.
Note that the plan was not done by a professional
, just a doodle to hand around to the guys to get them off my back that ended up being posted.