The dyneema and Dynex slings and runners by Black Diamond, Mammut, Petzl, and others have not been mentioned.
They've been around for a long time.Widths and lengths vary. Rated the same as carabiners, IIRC. And expensive, but just 5-8gm / ft if you cut them (ouch) into straps. Double that for the uncut loop.
Several flat, stiff sticks or, tongue depressers with clips to keep them from dropping, mounted vertically under high-strength cord at intevals around the tree solve your problem, and don't girdle the tree. Much lighter solution, what with a 6ft 2000lb rated Vectran or UHMWPE double eyed length weighing just 1/2 oz each.
For example: Cut a 1/16 groove with a rat-tail file, or a saw kerf, on each side of the tongue depresser. The tongue depresser then get mounted under the whoopie already wrapped around the tree. The cord catches in shallow grooves / kerf cuts, the way plastic bread-bag closure clips work, keeping them from falling off.
RE: Compliance, or taking it out of the system: This page by Yale Cordage is worth reading by everyone who mostly knows breaking strength and only breaking strength.
It is worth copying here:
Dynamic Energy in Arborist Rope
One of the most misunderstood aspects of rope selection is the disconnect between breaking strength and a ropes ability to absorb dynamic loads. Many people wrongly assume that the stronger a rope’s rating the harder it is to break. That is not the case as a rope can be parted if called upon to carry a load greater than its breaking strength or, if asked to absorb a dynamic load greater than its energy absorption capability.
Everyone is used to talking about a rope’s breaking strength but almost no one describes a rope’s energy absorption capability. This is obtained by studying a stress strain curve of load vs. elongation. The area described under the stress strain curve pertains to force acting through distance (or the work required to break it).
On the previous page you will find the bar graphs of our ropes’ dynamic characterists. The first shows each types’ working energy absorption which describes how much energy each will absorb before reaching its working load, which in the case of rigging ropes is 1/5 or 20% of its breaking strength. The more work the rope can do getting to 20% of breaking strength the longer it will last. A very stiff rope, with little or no elongation, gets to its working load without doing much work and quickly becomes loaded beyond its safe working load, regardless of how strong it is. These ropes are poor choices for rigging with the single exception where stretch cannot be tolerated, such as working with a zip line over a roof with limited clearances.