Digital BW, The Print

I'm thinking of getting started with a CFS for my 1160 and am 
trying to determine which inks to use.  I want to use the Piezo 
driver with MIS FS inks (for ink costs), but am hesitating between 
the FS and FS-N inks.  After checking out the step wedges on 
this site showing the blends and the regular wedges with FS 
and FS-N inks I've decided that a blend would be a good 
alternative to the coolness of the FS-N and the warmth of the FS.  

Now my question is, how will mixing the inks affect the fading of 
the inks.  Paul Roark's 300 hr fade test tells me that the FS-N is 
way more fade resistant (actually color shift resistant).  Will 
blending 50/50 between the two inks cause a significant color 
shift in fade tests?  Also, which inks need to be blended?  Just 
the 3 greys or does the black ink need to be blended as well?  
Are the blacks the same in both inksets?  

Thanks to all of you on this website.  You've all been so helpful in 
answering questions as I get started down this exciting 
quadtone path!  

Andy