I think you have done your homework well. May I suggest that you read the actual film for the census in question. You used the best way possible to determine if the enumerator wrote an e or u & that was to compare other letters he wrote on the page also. And it is possible that he wrote it the only way he knew if he did not know the name Hubbard too. Your comparisons in the published books are very astute. My opinion is that you are going in the right direction on this one. If you can find something he signed in the places he lived, that would be even better. Some of the best places are marriage bonds, petitions, probates & court cases. Keep us posted on progress.