After months of having his head slide back to the front, I figured that maybe if I turn his head all the way around, the peg would be loosened, and he'll have a greater range of view.
Bad choice, as his head tore off. It appears that the peg is attached to the body on all four sides, thus the "twisting" head articulation.
Luckily, his head is big enough to balance well on his shoulders, so I won't glue it. But maybe once we get a Bultar Swan, I'll use an extra for a Snivvian Jedi. She's short enough.