Derek,
Yes, nylon attaches the bicep to the shoulder bell in this picture. I had Steve do the same thing for mine. The nylon is glued using E6000 to the shoulder bell in the channel and the snap is put near the top of the bicep which will be hidden by the shoulder bell.
Just a nice way to keep everything in place.
And Steve, fantastic finish! So does this mean your available to work on my bucket?