QTR-Quadtone RIP

Hello all,

I have looked through the threads here and can't find that someone has
posted this.

I am using the above combo, and continue to get black, blotchy areas
where my images are dark grey. 

I have been using the Premium Luster (carbon and neutral mixed)
curves, which have this problem the least, but am still getting it.

I am having a very hard time wrapping my head around the curves
creation concept. I tried to create some curves by lowering the ink
limit, but then the entire image loses contrast. 

can anyone offer some help? Also, where might I find curves that I can
download for this combo?

thanks much

julie van dore