Chris,
Good photo essay.
I thought this was a pretty good related photo of a "similar" method.
I shot this pic Of my friend Penn. bonsaiman Jim Gillespie as he was repotting a prized Austrian Pine in a pot I made for him ,for it.
You can see how he used chopsticks driven into the rootball and then attached the hold down wires to the sticks. also, Nothing over rootball or on top of soil.
Regards,
Dale

Attached Images

Using chop sticks in root ball to wire down tree..jpg (60.4 KB, 82 views)

This is an excellent way to tie a tree in, especially on a tree with a dense, established root ball. Be sure to use bamboo chopsticks, as the pine ones rot too quickly.