Here is a pic of the base of the oak and ones that will show I hope the wound relative to the rest of the tree. The wound runs from 7-10m up this 13m stem.
The 2nd pic you can see the top of the wound where the Trunk narrows.
The 3rd pic shows a side angle; my TIP is 1m above the top of the wound.
Pic 4 is the top of the wound, with the only sign of active fungi.
Branches are sound and well attached; it is only the stem defect that is bad. Anyone who looks at this tree and sees firewood must also look at the Mona Lisa and see tinder.
quercus I think the necessary stretch can be accomplished with a dampening spring in a steel cable. I am disinclined to cobra due to photodegradation and squirrel predation concerns, as well as appearances and client (and my) confidence.