"Ian Jackson" wrote in message
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snip

Mark a spot 4-5 feet up on a tree, 20 years later it will still be 4-5
feet from the ground.

But won't the diameter, where you marked, be a lot greater? Anything
tied to the tree will get buried in the wood. Even if you leave 'room
for expansion', this may still happen. A tight loop, buried in the wood,
will also choke off the sap, and possibly kill the part of the tree
above.

I think maybe you could drill a hole through the tree with a wood borer.
The Irwin Speedbor toolset comes to mind. They can be fitted with
extensions for added length. I have two, 6" & 12". They use setscrews to
avoid the bulk of a chuck. Love 'em.

http://www.irwin.com/irwin/consumer/...brand=Speedbor

After the hole is through, slide in a piece of All-Thread, flange it with
some sheet aluminum (and maybe a couple of rubber bumpers to be a little
kinder to the bark) and add nuts. Attach your guy wire to the protruding
end of the All-Thread.

Trees will tolerate being drilled. I mounted a garden hose rack on a tree
about 20 years ago; tree and hose rack still doing fine as of this
afternoon.

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I didn't see this mentioned: Have you investigated the possible use of a
concrete "deadman anchor"?