The Plank Chorus appears in scene 201.
Like Vaughn's Chorus this one has 4 Flower Limbs, but has a simple WOODEN PLANK instead of a box for a torso and the Limbs are completely straight making it look more like a table. A Funnel Stack is secured to the bottom of the wooden plank. The Stack launches up a few inches lifting the Chorus and stretching the Flower Limbs. Then it slowly descends. CLOSE ON FUNNEL STACK: We see now that as the Stack descends it comes closer to a Controller placed far below it. The close proximity eventually causes the Stack to lightly launch again, lifting the Chorus with it. CLOSE ON LIMB: It compresses smoothly like it's hydraulic.
It seems that this is only a prototype, and gets no further mention after scene 201.