Franky, some good points!
my 2 cents: yes, Luk Achoi's Hung Kyun and Hung Heigun's Hung Kyun might have been the same, might have been different, but for us is no way find out. i know your Malaysian lineage goes back to Luk Achoi, but is does not necessarily means it is same as Luk Achoi's - during the generations after Luk Achoi it might have undergo a lot of major changes, exactly as Hung Heigun's gungfu or today's WFH/LSW gungfu - and the changes might be similar (and there are other things, like the question of pre WFH fhsyk, right?)
Jisin simsi was not a Northerner (and also not from the Northern Shaolin Temple), he was definitely Southerner, at least according to what i know. i mean, Fukgin is is North(east) of Gwongdung, but it is still South China. some sources say he has added the "long bridges, wide stances" to our "short bridges, narrow stances" after 3 visits of Gwongdung province, without giving much details why...
as i wrote above, for me is more than interesting connection between (old) Hung Kyun, Fukgin white crane and Wing Cheun, as already discussed here on the server, eg. here
http://www.hungkyun.com/forum/viewtopic.php?t=443 always going on in Fukgin always a story about a girl and the crane or connection to some female (Ng Mui, Fong Wingcheun, Fong Chatleung, Yim Wingcheun), always "short bridges, narrow stances"... damn, i really would love to find out more about all this
see you soon brother!