This next assumption will probably reveal my lack of understanding of the science and math of both RW and simulated SSS, but here goes anyway (my apologies if this is just reiterating what has already been discussed but I just want to get another angle on this). Can't SSS be described in terms of how far, and with what kind of falloff an objects surface will be illuminated beyond the terminator?
What I mean is this. When I've been looking at my VSS renders in an image editor what I typically want to do is to lighten, soften and (in places) add some orangy richness at and beyond that line, to simulate that light has gone beyond the surface responses and travelled through the skin. Given the .gif example above where I noted how with each image the terminator line was creeping further across the model, what I really want is (in a controllable fashion) for that line to creep in the other direction.

 

PoserPro2014(Sr4), Win7 x64, display units set to inches.

                                      www.danielroseartnew.weebly.com