Nice. I want to get a Sinden lightgun sometime. I guess I'm out of ideas since I haven't used one before. I thought I read on his site that you have to install some custom software or driver to make it work with the border around the screen.
Maybe someone else who has one might have some ideas. To me it sounds like there is some configuration specific to the way the lightgun detects whether it is pointed at the screen or not. On the original NES Zapper it would select game modes if pointed away from the screen and start one if it was pointed at the screen.