QTR-Quadtone RIP

Hi Guys, I'm trying to work out the procedure for producing an effective / accurate dot gain curve. I have access to an i1 spectro. 

I have read the User Guide from the QTR website, which suggests starting with values 6 for highlight and shadow, and Gamma=1.

However, there does not appear to be any information on how to go about refining the curve empirically (e.g. patch target to use + calculations etc...).

Any information at all would be greatly appreciated :-)

Lou