Rivet (button) 1.0 for Maya (maya script)

Hello,
I stumbled on your rivet script when I was looking for a solution to movement for snake scales.  I need to constain a rigid object (the scales) at a consistent point to a deforming one.  The script has been working great, but now further into the td process I have some other aspects that I need to resolve.   I need an additional constraint direction besides the vertex normal vector obtained from the parent polygon to dictate how the child moves.  The plan is to try and modify the script so that the secondary direction follows the edghe flow towards the front end of the object.  I am hoping I can take this vector direction easily from the edge itself, but I have a feeling it might not be that simple.  I have some limited experience doing this sort of constraint based relationship using dot products and cross products in houdini, but in Maya its a bit more challenging for me.  I am confident that I do only need one more direction though.  Any suggestions on how to resolve this?  I have attached several images on a low poly test object to give you a better idea.  The first shows the curve at rest in rest position, while the two second images show how the secondary curve deviates from the ideal vector position along the 'snakes' body surface.  
Thank you in advance