It can be done. Here is an example I did on a concave surface (a bowl shape).
You have to model both the male and female blanks exactly the same, just opposite (two rail sweep worked the best for me), then I used my own method of v-carving the female, then prism carving the male, offsetting the vectors by .08", and v-carving between the original and offset vectors starting at the depth of the prism cut (this just extends the cut deeper without affecting the original prism cut).
To make the 3D surface, just draw the vector and put the 'tails' going one way for the female part and the other way for the male part. You don't have to add .1 to it, because you want the BOTTOM of the male cut to match the TOP of the female cut. It will automatically turn out this way by projecting the cuts to the 3D surface.