3/16" flaps?? Too thin for that wing area, they most likely won't be rigid enough. I have plans, and I know it says 1/4" but, make them thicker. I make a box (AKA "lucky box) with 1/64 top and bottom plywood sandwiched around 3/32 lite ply. CF plate is even better. Make it nice and square and glue it to the end of the flap. Fill as needed to fair it into the rest of the material. When you install it, don't glue it. I'll be in Portland, if I can remember I'll show you mine.
That's one reason I don't build many kits. When I do the plans are mostly for dimensions.