Attached Link: http://www.morphography.uk.vu/modtut7.html

It works for me. I don't know the secret of making it work, but I believe it may help if the mesh is continuous, so that the welding process nominally has nothing to do. I say "nominally" because I hear that Poser splits groups into separate objects when it loads the mesh; but at least if your mesh is all of a piece to begin with, the welding is guaranteed to work. As far as I know. :) (Edited for spelling and style)