Hi BSR,
For this test I was actually communicating with my installed Z-Wave switches, from the USB interface in the metal foil box at my computer. The nearest actual device is mounted in a wall switch about six feet away so that would have been the one I was communicating with. The way Z-Wave works is that you only need to talk to the nearest device and then the signal gets relayed to your end device. That is why the remotes work so well. I cannot increase the distance unless I start removing devices from my network. I may try that at some later date, I just do not have time for that now. That is a little like un-linking Insteon devices, it gets complicated in that if you leave any broken links the network may slow down.
As I said, this is not real scientific, I have no idea what I did to the signal strength. I was just trying to clear up a misconception about metal boxes and Z-Wave. Metal boxes do not necessarily stop Z-Wave from working in any one direction.
Ken