QTR-Quadtone RIP

I am having some problems soft-proofing.

My setup is Windows XP, Photoshop CS and an Epson 1270.  I have 
created a curve using QTR v 2.3.10 for Kirkland Photo Paper with UT-
FSN  (but using the 3 gray inks only – i.e. not using PK). I am using 
QTR Gray Lab as my workspace with perpetual intent. I set up an ICC 
profile using the QTR-Create-ICC (both from v 2.3.10 and v 2.3 – I 
could not see any difference.).

The problem I am having is getting the monitor to match the output. I 
load an image and change the image mode to grayscale (I.e. Gray Lab) 
from RGB.
·	If I then "Assign Profile" using the ICC I made with QTR-
Create-ICC (in my case QTR-UTFSN-KirkPP-AllGrays), I see a lightening 
of the screen image which is then similar to the print.
·	However, if I set up a Proof Setup Custom using the ICC (QTR-
UTFSN-KirkPP-AllGrays), which I do without any image loaded in 
Photoshop, and check BPC, but not PW or IB, I do not see any change 
in the image. BUT, if I check Preserve Color Numbers (which hides the 
BPC checkbox) I see the same lightening of the screen image 
as "Assign Profile".

My question therefore is when using soft proof profile should I use 
BPC or Preserve Color Numbers, because it looks like the latter is 
being used by "Assign Profile"?

Any help is hugely appreciated

Keith Prue

PS. Aside from this I am having great output with QTR.