Digital BW, The Print

Hello everyone.

I just bought me a 3800 and printed some step wedges on Photo Rag with
ABW. Then I measured them with a densitometer. But the results were
not good. See the graph at http://www.xs4all.nl/~hc6/3800/3800.htm 

Although the largest part of the curve is smooth, the darkest parts
are bad, with no differentation between the 2 darkest steps.

My settings were:
PS CS: 
- Print space/Profile/ Printer color management.
- Working space: gray Gamma 2.2.

Epson:
- Media type: Velvet Fine Art Paper

Epson ABW:
- Tone: Dark.
- No further adjustments.

I also did a print on Velvet Fine Art Paper, which looked good, but I
want to use Photo Rag.
 
Could anyone, please, give me the right settings for printing B&W on
Photo Rag with the 3800? (if it is possible to make a good print on
this paper with the 3800)

Thank you,

Igor