2015-02-20 by richard@...
What printer, ink set and type of profile are you trying to create here?
There is a reason why the density option grayed out with what you said you are trying to do. The k curve, c curve, m curve, etc can be used to set the shape of the curve for each ink channel, but overrides any settings of the cross over points, gray gamma, gray highlight/shadow, and gray curve (But does not override linearization).
If you are setting Cyan to copy the K-curve then you wouldn't need to/can't set a value in the Cyan density option. You can set an ink limit for Cyan, and it will map the the shape of the K-curve to that max Cyan ink limit. The cyan density option is used to set the cross-over point with the K-curve to build the Cyan curve—trying to set a cross over point is a conflict with the copy curve option. If you change copy k curve to gray ink the density box will no longer be grayed out.
Richard Boutwell