Upper deck construction underway. I decided to go out on a limb (again) and use 9mm plywood (less than half the price of the 15mm of the lower deck and half the weight) along with the recycled 27Sq mm stringers. First section worked out well so I'll continue. Posted more photo's for you.
I'll try not to use vertical supports at the front of second deck if I can avoid it so the whole top deck is floating. I'm no carpenter by the stretch of anyones imagination but taking my time and measuring at least 3 times and then cutting it all seems to be OK using only a basic jigsaw. No tragic events yet!
Once again, Rail Modeller Pro has been invaluable in helping me design and execute the layout and I keep checking back to cross reference my design at all phases of the build. So far the entire lower deck is still visible with the top deck on when standing next to it so I''m pleased with the 35cm height difference.