@luvsmuzik: thanks! I already have the files somewhere. That was more of a accidental find, don`t know if I dig deaper into this.
For further-away-structures amidst real plants it may well pass, I think... and this network renders quite fast. Maybe it`ll be useful sometime, who knows.
@Kadri: Displacement Tolerance is now at 2. Render Time increased about a minute. But the error is still visible.
Anyways, I`d say it is better to get rid of the spikes or mask out the "bush" in question completely.
This setup is not worth long render times.
cheers, Klaus