I just purchased a new JD with this collection system and it works great but one small problem. How do you tell when the hopper is full? I was using a Hustler with the DFS system and it had a window at the top of the hopper, once you started seeing debris in the window it was time to empty. The JD does not have such a window but I was thinking about putting one in myself. Any tricks to tell when the hopper is about full?