Wong Mankai, a disciple of Lam Saiwing, wrote a short essay about "Tiger and Crane". he writes that fu hok seung yin kyun was developed by Wong Feihung.
the text will be available here in English, German and Dutch soon: http://www.lamsaiwing.net/lswmemobook.htm
i am sure that if it was Lam Saiwing who has composed the set, his disciples would give credit to him for doing so. Lam Saiwing was the one who popularised the set (and supposedly modified a bit), especially after the book on "tiger and crane", written by his other disciples, was published.
i have seen many "tiger and crane", but i am almost sure that they go back to Lam Saiwing or Wong Feihung. i have not seen any pre-Wong Feihung "tiger and crane" so far (except Wong Kiew Kit sifu's, which comes from a completely different lineage of Southern Siulam). anyway, any reliable info about pre-Wong Feihung fhsyk appreciated!