William, I'm not sure I understand your question about crossover lines. If you've entered your connections on Geni, then the info is there and Geni will calculate relationships based on it. Geni looks for the shortest path, so it might not display the line you want, but the line is there and can potentially come into play when you calculate relationships to other people in the same general area of the tree.
If you and Leslie both had an autosomal ("Family Finder") DNA test, you might find that you have some matching segments. The odds are increased because you have multiple Allen descents, but the two of you are so distant (8th cousins 1x) that the odds are against it. Even at the 4th cousin level, the odds of a match start to drop.
The DNA results reported at the Allen Project are yDNA results, not autosomal. With your interest in genealogy, you ought to have a yDNA test (if you haven't already), then perhaps follow up with an autosomal test if you're interested. Your yDNA results would help the project create a better picture.