Digital BW, The Print

I have used the procedure and files provided by Roy Harrington for 
icc based soft-proofing of B&W.  The soft proofs are acurate for 
images that are coming from ARGB, converted to gray, assigned gamma 
2.2 and sent to ImagePrint.

I would like to have the same soft-proofing capabilities for gamma 
1.8.  ImagePrint does a really nice job with G1.8 images.  The G1.8 
soft-proofing profile I made with the Eye-One and the same 
target/file do not provide accurate proofing.

What do I need to do to make a soft-proof profile for G1.8 source?  
Do I have to do something to the target or the .txt Match is looking 
at?

When starting with color images in ARGB space (G2.2) should I convert 
to another color space with gamma 1.8 such as Apple RGB before going 
through B&W conversion process?  Convert to G1.8 after processing or 
just tag the image G1.8?  I'm a little confused here.

Thanks,

Eric