The other thing that took a lot of thought was the general shape of the arm and the tool holder inside. Of course my first designs were akin to that of a revolver: round and with the tools of the periphery. I even did a few sketches of it but they ended up being as hard or more to fit stuff inside than the current model. Constraining myself to just the shape of a circle was hard and I always ended up going through the border: having two servos plus the chain just wasn't compatible with the geometry. The more "rectangular" shape the two weird holders gave me was much more comfortable. Nice extra too, I could extend the tool from the center of the arm instead of the border, which was a little aesthetic plus. 

Here's one of the attempts at doing this, note the chain storage part running down the side of the arm

I might eventually return to a rounder design for the aesthetic aspect, but for now I'm staying with my weird and overly complicated double barreled revolver design :D