Thinking about this; it would be handy to have some sort of mechanism/slider for the depth modulator to be able to restrict it to part of the height, say the lower half, of a cloud, with a soft top of that restriction. So if you increase its effect, it will not delete the entire cloud to the top.
That way you would be able to use even quite thin cloud layers to have an adjusted underside. In effect this would probably mean kind of the same as 'base whispiness', but with input at one's choice.