Digital BW, The Print

Hello from Iowa,
The discussion of MIS Full Spectrum with the piezoBW software 
inspired me to try it with my 1280.  First results were good, about 
the same as I have achieved with MIS VM-Hex and Paul's curves.  
However, with some of my wife's natural light headshots parts of the 
face are prone to slight posterization and with these images I have 
gotten much better results using piezoBW with their ink done on a 
friend's 1200. Then I saw Martin's suggestion to use custom dot gain 
to compensate for any difference between the inks.  This is looking 
like the missing piece.  Before when I tried to deal with 
posterization in the print by adjusting PS6 curves I only made it 
worse.  With the custom dot gain, I can minimize the posterization 
and at least match the quality of the all piezoBW system.  
Hopefully, more experienced users of custom dot gain can explain the 
way it works.  I am finding that PS6 on my PC with Win98 applies the 
custom dot gain in two completely different ways depending on how the 
image was originally saved in grayscale.  
Situation A:  The image is saved when color settings for Working 
Spaces Gray is not Custom Dot Gain.  In my case Gray was Gamma 2.2 as 
part of the Photoshop 5 defaults.  In this situation a Custom Dot 
Gain is applied to the image only when the grayscale image is opened 
and you choose to convert to the working space which is custom dot 
gain.  The effect of the custom dot gain will be seen in the print 
but not on the screen.  To make changes in the custom dot gain, you 
must close and reopen the image.  Moving the custom dot gain curve 
up, lightens the print even though black is to the right on the 
baseline.  
Situation B:  The image is ORIGINALLY saved when color settings for 
Working Spaces Gray is Custom Dot Gain.  The effect of changes in the 
custom dot gain will be seen live on the screen but will NOT effect 
the print.  Moving the custom dot gain curve up, DARKENS the print.  
If an image is first saved as a grayscale with Gray=Gamma 2.2 and 
later saved with Gray=Custom Dot Gain, it still behaves according to 
situation A. 
Any insights are appreciated.
Thanks, Hap