I was waffling on the diode or bridge for the reasons stated. I think you're probably right though, a bridge is most likely the safer choice. I guess I need to assemble a "feature list" to try to come up with all the ideas and then see how to fit them into a module. I knew the screw terminals would come up, it would be nice to find a reasonably inexpensive source for them. I suspect that the sandwich idea is also going to be needed, I don't want the module to get too big.