I can't find any explanation for why he's looking in Central America in the first place. If it's the 1842 Times and Seasons articles, then his rationale has disappeared now that we know Benjamin Winchester wrote those articles. If he is superimposing an abstract map, then that might make sense, but I don't see his abstract map in this article.
The abstract map approach is a good idea. In fact, my chiastic geography does sort of fit over Central America, albeit with some important problems.
At least Magleby seems to have considered several different areas, unlike Sorenson who excluded everything but his chosen area.
I like the way Magleby uses google Earth. Now if I can only get him to look a little north...