I think I've figured out how to properly install the wood 'crown,' that appears in the above picture, on top of my round peg post.
At the top of the post, I'll cut out some indentations, about the width of the 2''X4'' wood, perpendicular to and on opposite sides at the top of the pole. The whole thing will then be secured by a standard screw-lug on each side of the top of the pole, just as shown in the pictures above. In this way, after the 'crown' is secured by the two screws, the indentations will hold the crown in place, and prevent the weight of future dragon fruit tentacles, to collapse the 'wood crown' towards one side or the other.