To clarify just a bit (this info comes directly from the creative team)... the 'foam' is a high density, lightweight polyurethane compound that is very rigid and durable; the weight allows for perfect balance atop the bike, and the rigidity allows it to keep the nice clean lines of the pose. The 'articulation' comes at a few points: ball jointed neck, left elbow to help create the perfect contact with the bike handlebar, right elbow to allow for posing the gun arm however you'd like (and no breakage if you hit it accidentally), and knees to allow for perfect foot contact with the pedals. It's not articulated like you think of articulation in a 12-inch figure, but rather at very specific points of motion. On the bike, the pedals and handlebars will be metal for sure, and possibly other parts as well (he didn't specify).
The entire thing has been engineered pretty darn near perfectly, IMHO! Combined with the mixed media and cloth and armor, it all comes together for a very life-like look, as those of you who saw it in person at CIV know firsthand!
Watch for more information in the form of a behind-the-scenes article and new photos showing the different angles it can achieve with the head and gun arm. We have a long time before it ships, so we hope to present some really great content about this piece in the coming weeks and months! It really highlights the ambition of our Star Wars PF line thus far! :chew