Digital BW, The Print

Paul, I recently came across your article on softproofing using a gamma curve for black 
and white.  I have been getting superb results and finally not waisting paper.   THANK 
YOU.  You have no idea how excited I was to find this bit of information.  I do have a few 
questions though.  In your article you state this for step 7....

7.    Now you are back at the image file you had originally opened. Go to View, Proof 
Setup, Custom.  The new curve you made should be in the list, probably at the bottom – 
Select it.  Then check "Preserve Color Numbers."  The image on the monitor should then 
look like it did while you were making the curve.  Hit OK.

My questions is, I am unable to check "preserve color number" because it is grayed out.  
Am I doing something wrong?  Also, what should the intent be set to...perceptual, 
absolute colorimetric or one of the other?  

If my image is in rgb and I go to convert it to the softproof gamma curve, I get a message 
that says, "could not load the proof set up because the source and destination have 
different color modes".  So what I have been doing is changing it to grayscale and then 
converting to the sooftproof.  I have a feeling I am not doing this the way it is supposed to 
be done.  After converting to the soft proof, I make any necessary changes to the image 
and then convert back to rgb and print using the carbon curve you created.  The prints are 
looking great but I feel like I am missing a step or something.

Does this sound correct to you or am I doing something out of order?
Any help would be appreciated.  And thanks again for the advice you provide to all of us.

P.S.  I hope I made some sort of sense out of this mess.