IMO there can be plenty of doubt. The Shroud of Turin's veracity - or illegitimacy - is of no consequence to the truth of the Gospels. Playing "Where's Waldo?" with a piece of cloth only tarnishes that truth, IMO.
I appreciate the points you made in that post on the other thread, and I agree with you that the Gospel does not need the Shroud. But do you know much about the Sudarium? The Sudarium is from the same event as the Shroud - (whatever that event was, I grant you). The Sudarium, with its well documented history, proves that the Shroud is not a middle ages fraud.