Hi there,
So...this has bothered me for a looong time, ever since I started doing profiles, tried to fight it my way
but seeing there are people here with more advanced approach, I just need to ask.
Do weird too light or too dark lines occur to you too on the border of two masked area ? Here is what I am talking about
:

and
Mind you, I dont really use live spline masks in Photoshop, I make them in Illustrator and export the shapes to Photoshop but as rasterised shapes. Might this be the only cause ? Because no matter what i do to the masks, I cannot make them perfect (ok i can but then I have to go through every jagged line with a 1x1 pencil and paint each and every single faulty looking pixel )