He's cute but I'm wondering about something and will do my best to describe what I'm thinking ...
If he is held upright, rather than sitting, do his 2 face parts seperate? If they do, I wonder if he will look rather like an alien. His ears may become antenna and then you would lose the whole gorilla effect. If the face parts don't seperate, then there's no concern.
My thought on making the stem was to take a 1" piece of fabric and iron it in half, open it up, fold in the sides and iron those in, then fold it back in half again (like bias tape, just not on the bias).
Great minds think alike! That's exactly what I did for my stem