thank you patrick.
to me a serious disadvantage of a RIP compared to the printer driver i never knew about!
the printer driver uses only the 4 black/gray inks when i send equal RGB values. so totally neutral or at least metemerism free pictures are the result.
if the RIP doesnt… it is def. a point against using a RIP for fineArt printing.
besides that so far i have tried dozens of different black gens and am getting close to smooth gradients. still having a bump in the green. but i think it is more a problem of the swatch i am able to print and the ICC program then my black gen.
thanks for helping