Thanks ever so much Merlin and Al, that's exactly the kind of advice I wanted to hear.
Seriously though, that is what I had anticipated, but I needed confirmation from you good folk here on the fora.
Do I understand correctly that I could literally screw another SM40 onto the front of mine and that's what's known as "double-stacked"?
Many thanks.
Ps....anyone want to buy a Thousand Oaks or Lumicon Ha solar setup...going cheap....
Martin