Trondheim to New York - what ship?

I'm trying to determine on which ship my great grandfather sailed to
New York in 1883. He is listed in the Digitarkivet has having
registered to depart Trondheim on 16 May 1883 on the Cunard line ship
Hero.It seems that the Hero was actually owned by the Wilson line and
only sailed between Norway and Hull. I'm not sure if the Hero was
under contract with Cunard or just honored Cunard tickets. In any case,
as I understand it the standard procedure was to travel by rail from
Hull to Liverpool and then board a Cunard ship bound for New York. I
can't find a record of when the Hero arrived in Hull but it sailed on
17 May 1883 and the voyage should not have taken more than four or five
days. Given that and the fact that his 1896 naturalization papers state
that he landed in New York on 13 June 1883, I checked all of the Cunard
ship passenger lists that fall into that time frame and I cannot find
an entry for him nor his two traveling companions.

Is it possible that he could have sailed on another shipping line using
his pre-paid Cunard ticket? Was that a standard practice?

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