Typically on a enclosure that size a RHP isnt going to heat the entire enclosure, as the heat is radiating downward the substrate itself. Is this a retic cage? If so you could leave it like that honestly, give a nice gradient if they want to get cooled down. Mine switch from hot to cold side a bit. Cold end of my cages are about 74-75 with hot side right around 87-88.
Sent from my SM-N970U using Tapatalk