Predator Backpack and Cannon - Need help finding model parts.

[Art Andrews]

Here is one of the parts now. I am only looking for the piece in yellow (we have already identified the model around it). It is roughly 30mm (1 3/6") wide at its widest point. It is clearly some type of pivot point. I am wondering if it might be the hips for one of the destroid type models, but it could easily be a military type model piece. I could really use some help nailing this one down.

I will work on posting up detailed and large photos of some of the other remaining parts we have yet to nail down as well.