thanks for the answer.
Sadly for what you say I think the only possibility to achive what I want (continuity on mapping coordinates on final railclone object) it is to map the railclone object afterwards.
The original object is already mapped in a way that A and B surface do not share same mapping coordinates. But then, the resulting railclone object obviously has no continuity on the UVW mapping coordinates. I always have to map the railclone objects afterwards, but I was just trying to see if there is a way to not waste time on that and let railclone do the mapping.
Randomaizing coordinates by element is also no solution, as I am trying to get continuity on the mapping coordinates. Also using the "box mapping" on each element should do the trick, but with that I get same coordinates on both surfaces...so the question is, is there a way to achieve continuity and different UVW mapping coordinates in both surfaces?
ok, I realised that that happens when the elemnt in question is aligned in "bottom" on the y axes...if it is center, they share half of them and "top" are different, at least for this element size