Install Inkscape 0.47 pre release:
Wow! This is mind blowing!
To get quadrichromical images from Inkscape, our "rock in the shoe" way is to save vectorial drawing in SVG, and import it in Scribus. To get the right colors, we recompose svg-rgb colors in scribus-cymk. It's a fastidious work, and limitative, but it works very well. PDF we printed this way are perfect. We feared that new release of inkscape would disturb this way of proceeding. But we couldn't believe our eyes when scribus perfectly imorted spiro curves and generated a ready-to-print PDF.