Ordering the book of Jim marske must be a good idea. Mike Whittaker told me that he would have done his flying plank differently if he had this book earlier. Especially the data about the airfoils.I love tandem wings and biplanes, but I like a flying plank because it is in theory less draggy and this might result in a lighter aircraft.
I read an article by Al Blackstrom on nest of dragons. I have ordered Jim Marske book because he seems to enter into technical details regarding the aerodymamics of his slightly tapered wings; that seem very similar to a flying plank.
About saving weight with flying planks: i still dream of a flying plank which is so fat in the middle that the pilot fits mostly in it. Fat airfoils give the possibility to make a high spar whcih can be made out of lighter material. But the parts are longer too. I wonder if there would be a weight reduction by using fat airfoils. Anyway ... it will not be a speedy airplane if using fat airfoil. But i am not looking for speed. Just fun flying.
Control surfaces: if fearing stalls, go see the control surfaces of the Mitchellwing. NOT THE SPOILERS IT HAD IN THE FIRST MODEL (the hangglider in which the pilot was partly in the wing). The control surfaces that hang under the main wing. Might be draggy, but ... must be very stall free. Would it also give more stability??? Just to prevent tumbling.