Yes, it is made out of coroplast. The 020 heads are still available at $10.00 a pop from Cox. I have bought heads from Tower Hobbies in the $9.00 range I believe. Also, hit up the Local Hobby Shops. Sometimes you can find New Old Stock that has not been updated with the current price. I sometimes find Cox glow heads in the $3.00 - $4.00 range.
Here are some plans for the Grin Reaper. The deminsions are for 020 power, double everything for an 049. I use 18 - 20 ft dacron lines.