For the people that are new to RC and parkjets in general, the question always comes up - Does a flat plate wing work okay or should I spend the time and money to have a real airfoiled wing made? Great question.
One the things that makes parkjets so popular is the ease of construction. Throwing on a flat piece of foam and rounding over the leading edges is certainly a lot easier than getting an airfoiled wing made.
To be sure, they do have a little more drag and a little less lift than an airfoiled wing, but on parkflyer jets, the difference is barely noticeable, especially when you consider the time and cost of putting a full airfoil wing on your parkjet. Parkjets usually have swept low aspect ratio wings, high thrust-to-weight ratios, and have many elements that make the plane have high drag, like the intakes and flow-through inlets, so flat plates work very well and greatly simplify construction.
The answer to the question, without getting too technical...On these kinds of models, go flat plate and don't worry about spending the time and energy on an airfoil.