QTR-Quadtone RIP

Hello all,

I have been using PrintFix PRO to make icc profiles for UT-3D inks on
R200 printer. I am not completely happy with it, so I thought I'd try
QTR for more control. Even after reading all the manuals, it is not
easy going, and I am hitting a hopefully simple to resolve stumbling
block. When printing the ink separation chart, 3 darkest inks hit the
limit around 80%, while 3 lightest inks have visible increase in
density all the way to 100%. I am trying to create a simple 2-ink
curve with carbon and light carbon (C and LC positions; not using K
ink). Is it better to:

1) select 80% as overall ink limit, which would also reduce density
available in LC.

or should I:

2) select 100 for overall ink limit and 80% for C limit? If so, when
determining relationship between C and LC, should I match 100% LC
while looking at C printed at 100% limit or at 80% limit?

I assume it is desirable to use lighter inks as much as possible, as
they will have less visible dot pattern, which would make approach 1
better?

Many thanks for advice.