Hi
IamSam
I may have confused things by indicating I leveraged @peta64 psd file. I only leveraged the people part of the Layer and nothing of the Layer Style (they were reset) just so I would not have to start from scratch. Then I reordered the Layers, set the knockout setting, and then just used the Fill opacity.
I used an approach with the knockout and also using the Fill Opacity (and not using the plain Opacity at all on any Layer). This allows independent Fill opacity blending of each Layer (whether 2, 3,4, 5 etc) including the closest person Layer without any additional special instructions of using regular opacity. So was going for a simplified and more general solution.
For reference for those that don't know, the knockout allows the Layer to reach down and use a lower Layer as the direct Fill background to an upper Layer. If the background Layer is 0% transparent, then each of the Fill Opacity adjusted people Layers acts as Solid Layer, so one just needs the furthest back person as the lowest Layer, and the the next furthest back as the next Layer, etc. Since each person Layer is seen as solid, there is no transparency interaction with succeeding Layers. Each person Layer just overlays the next.
The approach I showed not only allows independent setting of the adjustment of the background color with each person Layer, one can also independently change the background color to an arbitrary setting and not have to go back and readjust any Blend IF settings. I have seen the knockout feature rarely used (limited capability) yet it does come in handy once in while.
Hope that clears things up (or did I just muddy the waters?

)