fok sao is a neutral elbow...neither tan /jum/jut etc...relaxed elbow occupying the center loosely ..ie after a strike we recover our arm/elbow back immediately to fok sao 'thinking' relaxed .
The wrist is nothing to do with it, why the hand flops down because there is no energy in the wrist after doing vu sao, the focus is the alignment of the elbow /wrist relative to the c line as it moves out to its position in SLT / centerline training drills.
fok doesnt dissolve
if you dont understand the idea being developed you get ambiguous ideas...like standing in a drill doing fok dissolving energy cr&p
. Think aggressive, attacking, flowing of techniques.