Oh, that's a neat set up in Joe's pic. I wonder how well that works. I love that type of simplicity in action.
I don't think the European cross-over assy added any performance advantage, just a cleaner appearance and presumably slightly less weight. If I recall (and I could possibly have this wrong) there are two versions of the European assy; one with a lower pipe and one with a higher pipe. If I'm not mistaken, the lower pipe was the earlier design and was found to be collecting raw fuel in certain circumstances. The higher pipe solved this problem. It would seem likely to me that by the time the Twin Cam was fitted to the (non-federal) Europa, the later design was being used. I caution again, though, don't take my word as gospel on this. Just trying to regurgitate a vague memory of something I once read.