The exterior of my house is made of frame hardboard. My wife says that I should not use it as a tennis wall because tennis size hail are known to damage the siding and therefore a tennis ball would damage it too if I hit the wall with the ball too many times. I say the material/object properties of ice and a hollow rubber ball are very different, particularly the coefficient of restitution. But I don't have any hard evidence that bouncing the tennis ball off the siding over many months won't do any damage to the siding. Any pointers? Thanks.