Digital BW, The Print

I hear great things about Baryta FB and bought 15 sheets to try out. I
do B&W (using channel mixer in PS rather than simple desaturating) and
use an HP8750. I've downloaded the profile for FB-Al and followed (I
believe) the settings stated in the guide that came with the profile.
There is something going wrong though... I am getting really weak
blacks.. I might call them "foggy blacks". Any ideas? 

Secondly, I can see fine scratches on the surface where the print
heads have swept across the print surface. I hear a lot about head
strikes... any cure for this with an 8750? Just as a "control" data
point... on HP Premium Plus Satin, I'm getting excellent blacks and no
scratches so I don't think the printer is in any sort of improper
condition. Thanks. 

Mike