I hate math. I use the freezer paper method too. One long piece of paper the length of the quilt and fold it until I get scallops the size I want. Draw my curve with the appropriate dinner plate or salad plate and voila, perfect scallops. My scallops are not the same on the short ends but no one has ever noticed. They usually end up with less than a 1/2 inch difference. I always think of my grandmother when I do it this way. She didn't have fancy rulers or a math brain either, just practical applications from her kitchen.