There is nothing like saying 'duck this, I'll just dive straight in and get started somewhere, and adjust from there, instead! So ahead we move, constructing the base from what materials I have available rather than plan and try to find what would then be needed.
Some of the support beams are pine, and they smell nostalgia to me, having grown up in the vast pineforests of the north. Memories of a hundred year old pineboard and fir floors, feeling them give with your steps, creaking and moving and scrubbed clean over and over through a century. Winters warmed by fires with sap crackling and shooting embers whenever birch was harder to come by cheaply, and the summer yard filled with the wood for the winter. Apparently, of olden times in Japan, they used mostly various conifers for buildings. I approve. They might not all smell the same, but so many have such a distinct warm aroma and a certain softness to the fibres.
Also, my Japanese razorsaw? One of the loves of my life.