The great thing about modeling is that you can easily test out different things. Why not build two wings, one with a flat bottom airfoil and one with symmetrical airfoil. Try them both and report your results here. We would love to follow your progress.

The truth is either will work fine. Each type of airfoil has it’s own set of advantages and disadvantages. After all, aviation engineering, like other fields of engineering, are all about “trade offs”. You never get something for nothing.