I do not want it to be said that your post here was not read and appreciated. As you say, the surname came to spelled in many different ways--often by persons of descendancy within their own lifetimes. Some Sickels descendants even added the "Van" to their names, just to confuse matters.
What Mr. Van Curen and I have to offer here is a strict adherence to both modern genealogical method and the concommitant view that the old sources need review and revision.
Concerning my own immediate Van Siclen family, about which both Bergen and Van Sickle fail miserably, one is left to try to understand why, since these descendants were alive and active during the production of both of these men's research. My branch of the family, which was important in the development of the New Lots area of Kings County, New York, (playground of Teunis G. Bergen, a resident of nearby New Utrecht, Brooklyn, who actually strolled the graveyard of these persons and made a report of same that was subsequently published) was not properly documented by either.
So, your Dad was quite right in his assessment.
Your assessment, however, fails when you denigrate the effort of both Van Curen and myself to make the same standards that your father was (apparently, and wisely) using in his assesments, of those previous efforts.
Mr, Gusman makes his assesments based, in part, upon the flawed assessments of both Bergen and Van Sickle.
Therefore, I would ask you to re-assess the thread about which you complain in terms of your father's misgivings.