Same curves. The offset function is 'subdividing' smooth curves as well, the result is that the 'forced' edges are lost and the artifacts are visible again. If I create new curves following the offset generated ones and add points where I would like to force edges according to the underlying original, then it works again. But that is a LOT of work. I downloaded TSplines last night and that deals with this problem perfectly.
Cheers
Lemo