your latest design has two wigs , right ?........how much more drag does that introduce ?. given that,....I would say you could reduce the airfoil thickness and maintain some decent deceleration. drag is exponential,.....two wings with a slightly thinner profile will produce more than "twice" the proportional drag than one wing with a slightly thicker profile.
let's stick to comparing apples to apples. and in a n above post you stated that a Clark Y would be a decent choice. I think the concept of designing the entire package to best use is pretty obvious requirement,...that said, discussion of aifoil section has to start somewhere no matter what complete system is being designed.....pick an airfoil and design a system around it, or pick a system and design the airfoil around it,...either way specific airfoil profile has to come into the process somewhere. so I don't see the point in your most recent post.