The Spade Fish[]
The search for the ultimate slope aerobat has taken many paths. One design that has shown promise is the "spade" fish. The basic idea behind this design is to maximize usefull side area near the CG of the wing, with the hope of making knife edge flight possible at slower speeds.
Cliffhanger (RCGroups) has experimented with this design in his series of X-Centric gliders. These "odd" looking gliders fly knife edge almost as well as upright/inverted!
Michael Richter (Dream-Flight ) has combined with Steve Lange to prototype a spade fish design called the Aero Glide. This design also incorporates a full flying elevator and rudder. The Aero Glide has been able to do elevator flips as well as the first ever documented rudder flip!