Guys, I gather this pertains to his tethered kite thread from a couple of weeks ago.

Modern sailplane airfoils are in that size range and certianly offer more than a 10:1 ratio. How critical they are to shape cocerns vs L/D values is something you'll have to do some experimentation on. I believe that the speed range you want to use them in is within the ballpark of the research done on true sailplane flight. If you look into that area you may/should also find a wealth of wind tunnel data on those airfoils for that Reynolds number and the surface roughness and profile tolerance they will withstand. I know the tolerance is not much but I don't know by how far.

You've gone outside the pervue of the modelling area with this one. Good luck.