My partner and I are making several 6 volt positive ground devices. So far, we have made a "black box" that allows you to run any 12 volt negative ground device (iPod, GPS, backup camera, etc.) on a 6 volt positive ground system. We also make a similar device that allows you to run a 12 volt negative ground tachometer on 6 volts positive ground, (a much more complicated task). If this looks like something that is needed, we could look into developing such a device (this is assuming that such a device of sufficient quality doesn't currently exist).