Dick,
Regarding flat plate airfoils, I recall back in the late 50's or early 60's NASA or it previous incarnation experimented with a flat airfoil for use in the hypersonic region, I think it's designation was NADA or something along those lines...
The one thing I remember is that it actually worked fairly well for them, it was essentially a flat plate that had a rounded LE and tapered TE, and other than that just a flat plate between.

I can not wait to see how my "flat plate" airfoil works on this one at 2 lbs AUW on 516 Sq inch wing.