Well you can indeed use the SVDL method in Vue to create displaced second skins but you are not going to get results as good as using a specific grayscale displacement map.  Here are a couple of pointers however on how to replicate the SVDL method in Vue:

1.  In Poser, Black represents a displacement of zero whereas in Vue it represents a negative displacement.  Zero displacement in Vue (and most other graphic programs) is represented by middle gray.   So you will need to normalize the computed displacement map in Vue by using a "Map" filter to set all black values (-1) to zero (0).  Plug a map filter node into the computed displacement map and set the values as follows:

Input Range Lower : -1
Input Range Upper: +1
Output Range Lower: 0
Input Range Upper: +1

2.  In all likelihood, you are going to get displacement artifacts showing up using SVDL's subtraction method due to jpeg compression pixelation issues.  You can smooth some of this out by using a "Quantize" filter and then playing with the threshold and contrast settings.