Thanks, everyone. I think that I will start with one 120 back and then keep in mind the idea of adding a second as a way to help me problem-solve time crunches, lighting issues, etc. (unless the store happens to have a used 'kit' with more than one 120 back; wouldn't that be convenient?). There's a wealth of info on this forum. Thanks so much for taking the time to offer some of your thoughts and experience to help me. Now I'm going to start a thread asking y'all why you chose MF in the first place ....