Thanks for the reply however I believe you misunderstood my question.
Attached is a bicep build from the AM armor tutorial. I have already removed the return edge from the top and bottom of both the inner and outer bicep.
If one wants to build the AM armor using the butt joint/cover strip method instead of the overlap joint method then you would follow the directions in the tutorial. If you want to follow the overlap joint method then you would, in this scenario, simply insert the leading edge of inner bicep into the notch of the out bicep that represents the cover strip on the outside of the bicep (see picture where the black arrow is pointing).
As the AM armor is designed to use the overlap method due to its construction, I wanted to try this method. However, after trimming away the return edges (both top and bottom of both the inner and outer pieces) I found that the bicep was way too large (see my original picture) by about 3 inches.
To make the bicep smaller, my statement in the original post was this: you cannot cut the section highlighted in red because that is the downward slope of the inner bicep notch. If you did cut this section, then the inner and outer bicep pieces would not match up.
The logical place to cut to make the overall bicep smaller is the green section BEHIND the integrated cover strip on the outer bicep piece. In my situation, as I need to reduce the bicep size by a large amount, it would mean that I would have the remove the cover strip entirely, then cut into the green section behind it to reduce the size of the outer bicep piece. Then I assume that I would place the entire cover strip that I previously removed over the joint between the inner and outer bicep pieces.
This seems like a lot of work and I was wondering if anyone else has used the overlap joint build method and had to deal with a similar situation of having pieces that need to be reduced in size by a large amount.