I think one clue is that tan and bong are somewhat mechanically opposite of each other, almost as if they were the same technique performed forwards and backwards in time (this would be literally true if you switched a regular tan out for a sinking tan or "tun sau"). The question then would be...
I'm not properly caffeinated yet so my analysis of this post is probably lacking, but this perspective has always baffled me.
Yes, there are a million and one things that you technically *can* do with all of WC's tools. Yes, you can, technically, if you go about it a certain way, use your bong...
I'm having a hard time visualizing this so I can't really provide specific input, but I would investigate why you're trying so hard to hold your bong sau position against that much pressure - bong is somewhat of a transitional technique and isn't really designed to be able to absorb direct...
It seems rather counterproductive to me to try and force Chi Sao to do things it wasn't designed to do in order to incorporate half-assed grappling rather than just learning proper grappling to begin with.
I got bored and am trying to make a list of all Southern Chinese short-bridge styles AKA Nanquan. Anyone wanna help?
What I got so far:
Wing Chun/Weng Chun
Hak Fu Mun
Choy Lay Fut
If you receive force that's best responded with to a bong sau, sure.
What's seen in the video isn't a bong sau though, which is important because bong is actually an incredibly weak position in and of itself which certainly shouldn't be held for any length of time and certainly not as a barring...
The idea that Wing Chun was practiced on the red boats has largely been debunked as a myth from what I understand, although you'll find plenty of different groups out there who claim to be the red boat style.