Hey Treecharger,
I hung my first PV in a tree many years ago. In my early days Mark James and I had a contract with a local electronics company and we did TV antenna's for them once or twice as month for a day...we went house to house topping and bolting the antenna's to the tree...still pretty common to find the remains of such installations in trees here in the PNW.
We always told folks that the tree would beat their antenna to death soon if they did not have us back to manage.
I would suggest looking at some of the innovations that the tree house building gang have come up with.
The trick is to install with room for many years growth of the tree, also I think important to have client sign up for regular management of the new growth.
I know Orcas well...lived there for a while...still visit often. Contact me off list and I can give you some specific advice. Scott