As far as material choice, this is my first time designing a game object manipulator. Up until now, I've been the drive train guy.

The extrusion for the arm is 1x1 with 1/6th inch wall, at 24 inches long, and the sliders/brackety things are made of delrin, and are 1/4inch thick. I'm probably going to make the thing smaller, but with the grabber I play to design onto the end... I might need to make it thicker. This grabber should be able to passively "slurp" up about 4-5 inner tubes at a time, and then spit them out onto a post. Now all of this is speculative of what I think the game will be.