I've answered the thread you linked, narcissus; however I don't think it applies exactly to this query. I was suggesting that the original model should be mirrored when it was being made, and in that instance the facet/UV relationship would be mirrored too. Of course, there'd still be the challenge of stitching the UVs back together; and you can't apply this method to a model which is already made. I never said it was a good idea. :)