QTR-Quadtone RIP

I'm a QTR user on Windows XP, 1160.

Just loaded a 'new base' PK in a K position to print on glossy (kept
UT-VM set in color positions).
Since my dark gray has a higher Dmax than PK (as per ink separation
page) I'm thinking of using the UT-VM dark gray in C position as my
black.
I could, of course, refill the carts but short of that can I create
the curve by setting the C density to a 100 and PH in K would be 66%
and M 20%.

Would this work or K position allways has to be occupied by the darkest 
(black) ink, all the other gray inks' densities being defined as a
percentage of K ?

What about 'Boost K' ? Obviously there is no 'Boost C' ? <g>

Any insights appreciated ..

Roman