I was going to say that some times with silicone it is a pain to deal with inevitably a piece or two falls off and there is no way to fix it...any way i say this i have built a bunch but never with the spray foam thing hich gave me an idea... what about using magnets? can you use those rare earth magents covered with foam to keep in place?
Great idea...I have some and they are pretty spendy. I use them in my classroom to teach. The silicone method has worked well in the past and is pretty cheap. I think I am going to try the magnets with some other pieces and not the background. It would work great for root systems that I want to remove for cleaning and maintenence......great idea! thanks