Generate Complex/Face Group issue

[steveF4BW3]

I'm trying to take apart a model so I can create a multicolor .3mf file. I have successfully split several portions but I'm now getting to a point where nothing seems to work.

First I selected the next section:

Made it a face group:

Clicked "Generate Complex" and double-clicked the black border and get this:

Pretty sure that's not right. When I accept, I end up with this:

I was expecting the entire area that was selected and part of the face group to be shown here.

I'm definitely new at MeshMixer but thought I had it all figured out when I was able to remove several parts. Pretty sure I'm missing something fundamental.

For reference, here's the full model. I've removed the helmet and the bones sticking out where the arms and leg were before King Arthur and his Knights of the Round Table cut those off.

[steveF4BW3]

I think I now know why this is happening but don't know the solution. I need to have Meshmixer select deeper into the object so that it can get all the material which is at different depths. I can't figure out how to make it select more material deeper into the model. Google says use "Extrude" but that actually extrudes the material selected (inward or outward), rather that extending the selection area deeper into the model. It's like if I wanted to just select a circle and pull a cylindrical plug out of the object, but in this case it's not a regularly shaped cylinder.

[hfcandrew]

Sometimes you essential need to manually adjust the complex surface so it bulges how you want: https://forums.autodesk.com/t5/meshmixer-forum/when-i-generate-a-complex-it-fills-in-a-section-i-wan...