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"Hoist" ropes tied to the ends of the antenna run through pulleys to cleats nailed to the tree near the ground. The pulleys are attached to "support" ropes run through the tree crotches, and tied-off on the same cleats.
At first, both hoist ropes were were tied-off, but this doesn't provide any "give" when the trees blow in wind.
I removed the north hoist rope from the cleat, and added a weight. Now when the tree moves, this weight moves up and down to prevent over-stressing the antenna. The weight originally was a concrete block with a 4"x4" hole in the center. But it was too heavy even after cutting off about 25% from one end. When I tried to cut off more from the other end, the block broke into three pieces. I tied the largest of these to a 2x4 support, and the resulting weight supports the antenna just fine.
As part of this modification, I pulled the north pulley closer to the tree, raising that end of the antenna approximately five feet. The south rope is stuck in its tree crotch, and will require two people alternately pulling on the rope to loosen it.
Daughter Miranda helped me free the stuck south support rope, and I raised that pulley several feet. With both pulleys closer to their tree crotches, the antenna feed point is about four feet higher.