Hi Rooster, I considered that but I couldn't think of how to do it.
The tree is pretty large already (weeping willow, ~3' diameter, topped off by a storm at ~25' and now putting on a new "head of hair"), so I'm hoping my radial beam arrangement will work for a decade or two. As the tree grows I think I may need to trim the innermost decking, so that it doesn't strangle the tree. I plan on leaving a ~3" gap between the deck and the tree to delay this eventuality.
At some point, I might need to loosen the lag bolts a bit, to relieve compression on the support blocks as the cambium grows outward. I might even need to replace all the decking/rails eventually, lest they get slowly driven into higher and higher tension.
On the other hand, I have read on several tree house sites that trees often grow around support structures, especially if they don't make a band around the tree [which is considered bad form], just slowing enveloping the supports in cambium/bark. That's why I went with radial support beams (even though they're really a pain to attach to the tree!)
I'm too far into at this point to do a major redesign, but I would be interested to learn how what you suggest might be accomplished!
David
