To me the "flaming ramparts of the world" are exactly the outer shell of our cosmos/world-system described by other philosophers of the time. The outer shell - the outer wall/ramparts - are on fire. That's what makes the stars shine. 2:1144 also uses the "ramparts/walls of the world" moenia mundi
Accepting, as we do, the significance that the "walls" can be little more than currents/pressure and, even if more substantial, can and will breakdown into the infinite space beyond them, I must agree that we have the typical high tolerance for various possibilities:
(DL X 88) "A world is a circumscribed portion of sky, containing heavenly bodies and an earth and all the heavenly phenomena, whose dissolution will cause all within it to fall into confusion, it is a piece cut off from the infinite and ends in a boundary either rare or dense, either revolving or stationary: its outline may be spherical or three-cornered or any kind of shape" (Bailey)
"A world is a circumscribed portion of the universe, which contains stars and earth and all other visible things, cut off from the infinite, and terminating [and terminating in a boundary which may be either thick or thin, a boundary whose dissolution will bring about the wreck of all within it] in an exterior which may either revolve or be at rest, and be round or triangular or of any other shape whatever. All these alternatives are possible : they are contradicted by none of the facts in this world, in which an extremity can nowhere be discerned. (Hicks)
Thanks for the citations. So, Epicurus is talking here in 88 about a κόσμος (cosmos). I agree Epicurus is willing to entertain various shapes for the cosmos/cosmos/world-system/visible universe. But the important thing is that the cosmos is delimited portion of The All (the universe) with a definite boundary ofsome kind enclosing it. Epicurus used his imagination andreasoning and observation to "fly" beyond that boundary out into outer-cosmic space and share what he learned. So, by definition, IF the gods live in the space between cosmoi, they, by the definition of intermundia "between world-systems", they have no world to stand on nor stars to see. There's obviously some matter in that space between worlds but not enough to have a world, otherwise the gods would be *in a cosmos*.
btw, I have no idea why I'm so fixated on this. I don't believe gods exist in this physical, metacosmic way... Basically because the universe isn't built like this... Like I said unless we go with the multiverse. Even then, we would have no way of accessing the intercosmic/multiverse spaces. That's why I continue to take the Sedley "idealist" position on the Epicurean gods as I understand it. I can at least reconcile that to both a classical and modern understanding.