I believe you raised this question before in a slightly different form. As it appears to be for soccer or "football" in international terms. My question is: does it need to be a "solid" target? In soccer the score actually occurs when the ball passes through the front rectangular portal formed by the front frame of the goal and the ground. It seems to me that your problem could be addressed by using am RFID card equipped ball and goal frame sensor with a shallow net to catch the entering ball.