Well over half of the individuals who contact me state that they want a multi-deck layout. The idea of doubling the size of the potential railroad seems like a silver bullet. The decision as to design configuration is neither good nor bad IF you know exactly what the pros and concerns are. That's my concern. I really don't think most people are going into this with their eyes wide open. By not doing so they leave themselves open to spending many thousands of dollars on what amounts to an unworkable dumpster fire. I spent today writing a dig deep discussion on the subject which you can read HERE. Be forewarned that this is not light light reading. It's not entertaining reading. But, if you're seriously contemplating spending what would likely be a decision costing well over 10k, it's worth going through. Multi-deck layouts have their place. They are the right fit in some circumstances IF you know what you're getting into.