2-sided modeling problem

[Marko74]

I am getting some puzzling behaviors from my model and can’t seem to figure out wat is happening and why. Let me explain: As my first try at 2-sided modeling, I am attempting to model a wooden mask. I am working from 1” thick material.
The top side of the mask consists of facial elements including two eyes and a mouth which are meant to be holes that pass through the mask and are, thus, modeled as “Subtract”. The other elements protrude positively and are modeled as “Add”. The intent is that when the CNC router cuts the backside of the mask in a concave contour, the eyes and mouth will be revealed. Image #1 reflects the Top Of The Mask.

For the bottom of the mask, I modeled a closed vector which is slightly smaller than the circumference around the outer boundary of the mask so that the concave portion of the back of the mask starts inside a quarter-inch or so of the outer perimeter.
The topside of the mask’s model is complete and looks like Image #2

Following the instruction from the tutorial video “2-Sided Marlin” after completing all elements of the top of the mask, I created level for the combined model and created a copy of the combined model so I was able to smooth the contours and such.

Moving onto the back of the mask, after modeling my concave surface, I can see the eyes and mouth showing through from the front side while toggling the double-sided view button: See Image #3

However, when I create a “copy of visible model” my view shows that I have cut too deeply into the back of the mask and have compromised the top of the masks details. I thought that by creating the “Copy of visible model” I will incorporate all levels including my Tabs so that when I create my cutting paths, my tabs will be effective. Why do these two views so dramatically differ?

I tried to attach a copy of my model, but it was too large...

[highpockets]

Try working through the Creating a Spoon Tips & Tricks

[Marko74]

Thanks for directing me to the Spoon video. It helped. However, the explanation was a bit vague in the video. Let me see if I understand it correctly: If a model has several levels...say...
5
4
3
2
1
And say most of the components of the model reside in level 1. And perhaps tabs in 2, and other elements in the other levels...Then, while generating the toolpaths one chooses to set "Machining Limit Boundary" at a "Selected Level". If level 1 is chosen, then the toolpaths will entail all elements in level 1 AND all elements in 2, 3,4, and 5. If say level 3 was chosen as the "Selected Level", then the toolpaths will entail all elements in levels 3, 4, and 5, but NOT levels 1, and 2.

Is that correct?