Yea schrauts design is good but a full airfoil size airfoil is much better. I am building my own wing with a pw108 airfoil. Some other guys made a similar wing with the same airfoil, his top speed is 100 km/h.
why not try a dswing . its a foam board build with kfm 2 foil .
i have just finished the design for a simple 2 sheet design. the design includes folded foils and a locking design .
its a 700mm design which is a bit bigger than the 24 inch dswing i had .this one will be built from 5mm foam board for a better foil step.
Flying wings are simple and fly great if you get the cg within range. No need to go full airfoil, but I've been told I'm an airfoil diva, so I do. Like Ninja said, Clark Y works just fine, just trim the elevons up for reflex.