Large southern live oak limbs do require additional support that matches the loads they will experience. Unfortunately, there is some disconnect between installation, materials, and hurricanes. I will not comment on the ANSI A300 standard because it is not in front of me and I have not read the cabling section from the 2023 revision. I do not currently cable and have not for 3 or 4 years.
You need to have a green log weight chart. Southern live oak is about 5/4ths the density of other oaks in the area, and even more dense than pines. You should estimate the weight of the limb so that you know what you are dealing with. Then consider the force of that weight in the wind, and gravitationally when it gets wet. If you choose to install metal cabling, chances are that it will fail in a hurricane for two reasons; the largest metal cabling spec does not provide enough support to a large live oak limb, and when a hurricane comes along the flex in the limb will unweight the limb, putting a dynamic load on the branch when it is reweighted, which is a weakness for metal cabling. You cannot make the cabling tight instead of taut to prevent this unloading because the large diameter is not capable of being winched up, and because the ANSI standard likely still says "taut". If the metal cabling breaks, the limb is in a compromised state because the longer the cable was installed, the more the tree became dependent on it for support during ordinary conditions. Now it is unsupported during above-ordinary loads. For this reason, the only material that I am aware of that is suitable is the product sold by Wesspur - a dynamic cabling system that is rated by the manufacturer for very large loads. Dynamic systems, however, suck because of cultural factors - the owner moves and the next guy does not maintain the cable, or the arborist moves on. End of the day, tell me how you are going to service a very large tree over its life span - you probably will not. I am acquainted with two very large southern live oaks with metal cabling systems and both broke. I did not install either of them. I did not see the initial installation, but the tiny cables look undersized next to the wood.
Southern live oaks of largest stature often grow in sunny locations and this means that they are about 75-85 feet tall and spreading much more than that. The spread often means that there is little in the way of a central leader, and it can be tempting to install the cable much lower than 2/3rds the way between the crotch and the tips. A 2/3rds installation can even have the cable running under the branch it is supporting in order to make it out that far. You need to have a narrative to justify installing it at a lower location - one that is defensible in court.
The other problem with very large live oaks is that if they appear to require bracing you may need a very long bit. American Arborist supply can make a bit that is 15' long. The room where their kit is will not accommodate a longer bit. They make the longest bit I am aware of. The bit is 2' of fluting and 13 ft of shaft. When the flute exits a trunk it falls down onto the shaft before you can get it in the next trunk, so it's a bit difficult to drill. The shaft is also subject to torsional and bending forces that are greater than they are for shorter bits, so have a plan for if the bit breaks. In part, you should have a lithium-powered drill with a clutch, made by Milwaukee (superhawg, not hole hawg) or Makita's new version which this forum reports is more powerful than the Milwaukee. This keeps your thumb from getting ripped off when the bit jams in the wood, and may keep the bit from breaking as well. You will need some plan to either use multiple bits or to support the long run of shaft between the drill and the tree. Be careful of extensions since the attachment may be greater diameter than the hole, and some types of attachment may come undone inside the tree.
End of day, imho, try to reduction prune the largest southern live oaks in 4" diameter wood, dead wood them, prune trees next to them to provide access to sunlight for the ends of the low branches, and mulch them. This is a love and leave specification.
. Looking at the ANSI minimum hardware standards I realize that the chart maxes out at 30" dia. SLO do have branches over 30". Questions:
