Actually, Kamil, I've since made contact with somebody here who is really experienced in raising hynobiids post-morph so I think I'll gather tips from him and give it a try (especially seeing as I have 3 kinds of H. larvae brewing already)
In fact, I'm planning to get a used glass door cooler, the kind soft drinks are stocked in at your local 7-11, for use over the summer months to keep them especially cool like you mentioned.