Digital BW, The Print

I have been trying to use Brandin workflow for Quadtone printing thru 
the RGB space as per MIS site instructions.If I follow the workflow 
to the letter the results are very disappointing,but if instead of 
using photo paper in the Epson driver I use Glossy Film the output 
improves considerably. With the Photo setting the problem looks like 
black bands running the same direction as the print head.
Any explanations and why have the settings worked for others?
PS I am using a Epson 1160, MIS standard ink set,PS 6.01 PC,EAM and 
Somerset Velvet papers.
Regards to all on the list from down under
Tony