Void and space in stoic ontology

The Stoics claim that the cosmos is a finite plenum containing all substance within itself, but also that it is surrounded by something: namely, an infinite expanse of void. The standard scholarly view has been that the latter claim is forced upon the Stoics by their own physical theory (in particular, their view that the cosmos will eventually expand in size.) I argue the claim is rather the consequence of a Stoic commitment to absolute space, the unoccupied "part" of which is void. I then consider how this commitment fits in with (or at least fails to undermine) the Stoics' corporealist ontology.