Have faith. It'll bend. I have my Dutch with the M16 slung over his back and his other hand bent in front of him, holding the cigar. This pose requires both arms to be bent inward at the elbow.
Wait, so you turn it side to side literally at the elbow? That's probably where I ran into my roadblock, I'd bend my elbow 90 degrees, then try to use the forearm as a lever to rotate the bicep. The Rambo body has a bicep pivot like most regular bodies so I assumed if Dutch's could move that way, it would function the same way.