Actively constructed subjective imagination cannot be confirmed nor contradicted. 'I imagined it therefore it is', is not compatible with Epicurean system.
I think it can. Dreams are real. We don't choose our dreams, they just happen.
Dreams are real in the sense that they happen to us but what we dream about does not automatically become true in Epicurean system. 'I imagined it therefore it is' is not compatible because it's a simplification that can easily produce errors. For Epicureans, the claim that we create our own gods to represent our ideals therefore such gods are real would fail under the scrutiny of their theory of knowledge. Epicurus explicitly talks about this here: (Letter to Herodotus, section 51, Yonge's translation)
In fact the representations which intelligence reflects like a mirror, whether one perceives them in a dream or by any other conceptions of the intellect, or of any other of the criteria, can never resemble the objects that one calls real and true, unless there were objects of this kind perceived directly. And, on the other side, error could not be possible, if we did not receive some other motion also, a sort of initiative of intelligence connected, it is true, with direct representation, but going beyond that representative. These conceptions being connected with direct perception which produces the representation, but going beyond it, in consequence of a motion peculiar to the individual thought, produces error when it is not confirmed by evidence, or when it is contradicted by evidence; but when it is confirmed, or when it is not contradicted by evidence, then it produces truth.
