The Treehouse - Flying the floor
The plan was to pull the platform high enough into the tree so that the lower ends of the headers were above the supports. Once it was up there, we could use other ropes, already in place, to spin the frame counterclockwise (from the perspective of someone looking up at it from underneath) and let it down so one header was outside each support. We could then slide the assembly forward so the plywood was up against the Western (near) tree. At that point, we could lower the other end until the platform was lying flat, with its 8-foot joists crossing over the large support beams.
I expected that if I got a couple guys together, and we pulled on the ropes, the platform would just rise up between the trees. But it was too heavy and there was too much friction at the tree junctions for it to work that way. Instead, Kyle and I had to push the platform from underneath, first with our hands, then, when it got too high, with long boards. Each time we'd push, Steve and my wife, Ann would take up the slack in the ropes and tie them off. Then we'd push again. Eventually, we got it up there. It took about 2 and a half hours.