The Del Mar map isn't even authentic (Everyone by now accepts this as fact) , and not that old. It is one in a series of fakes that have served the wild imaginations of those who could easily, and difficultly (!), see through them to serve their deepest desires.
What Blankenship settled on evolved. He scoured the world looking for a story to fit his delusion. Some of the notable things he favored are the Concepcion salvage and the alleged Lord Anson (Spanish shipping of the ark) mystery folklore. How it ended for Dan was not with those theories. Dan was under the influence of his American friend Betty McKaig in the 1970s who had continued the 50+ year investigation of the Baconian scholar Leonell Strong into a star mapping theory based in the Northern Cross asterism's presence in the constellation of Cygnus. During these years his interest aligned with those of David Tobias who had DeVere, Bacon and Shakespeare in mind. Out of it came a loss of interest in the MP workings. We know he shifted to the hole he called 10-X. The name itself is evocative of ideas in the McKaig theories. Both 10 and X have the same value. This is a theme in the Shakespearean masque suggestion where we have two faces for one reality. The sum of 10 and X is 20 (anciently twenty from "twin t"). The twin T mystery is Strong's pet mystery. It refers to the Triple Tau and its explanatory value in understanding the mystery of life and death. The product of 10 by X is 100 which was understood by Strong to be the Tudor cipher value of Francis Bacon (add up the positional value of the letters in the 24 position alphabet, 67+33).
After Tobias left with his money Dan floundered. He basically hand dug 10-X until the Laginas showed up and reinvigorated the much older theories of countless brain dead scoundrels.
This is not to say any of Strong or McKaig's research has merit. There is nothing in it that implicates OI over any other place except that OI already had an aura of mystery which had shifted there from another local island (Hobson's Nose). The shifting of the story happened between 1830 and the first searcher efforts in the 1840s.
I implore you stop to inventing shit up based on things long ago discredited and spreading it confidently.