There seems to be a tendency to match the subject with the evidence instead of the reverse. This is the wrong way to solve a case especially one like the Zodiac case. You will find all kinds of weird combinations that appear to be right but all are not right. This type of thinking leads you into circular patterns of thinking which eventually lead you to the wrong person or persons. You must take the evidence and  set aside the person or people you like until you have assimilated all the evidence and then try to make a match with the best subject. If you don't you will have an almost impossible job of getting rid of subjects that you don't  want because your mind keeps slipping back into old patterns of thinking. I think this is what happened in the case of Arthur Leigh Allen. Also he didn't help things any because he kept taking responsibility for crimes he probably didn't commit. Of course there is the theory that he might not have known he was the Zodiac if in fact he really was.