Thanks to rg's suggestion, I just added a small segment of one of my climbing ropes to the tree anchor at the top of Beginner's Delight.
But it was a single-rope instead of the suggested half / double rope. And I don't know if that tree is disapproved for rappelling - (or if the tree about 20-30 yards southwest along the GT ledge from below it is approved or disapproved) - so Please may those with greater experience and judgment in there matters advise me about whether I should go back and remove that piece of rope.
I do know that with double 60m ropes it is possible to rappel from that tree all the way down to a ledge with a short easy scramble to the ground. I also know that it is then possible to have difficulty retrieving the double-ropes (fortunately I was able to learn this by watching another party).