My place is about the same temp. I run a dual system 2 UTH (two t-stats) and a fluorescent light inside with a blu led night light.

The uth keep the surface temps and the lights help bump up the air temps. I add blue or pink foam insulation to the top and sides (not blocking the vents) to help hold the heat. To be honest the cool side uth is rarely on. I am currently have two test enclosures one with just one UTH and lighting one with a radiant heat panel. They are performing ok the RHP is a bit temperamental to get stable. some have suggested placing the probe under the substrate but with the air temp I have been playing with the panel and hide top gets SCARY hot (100º+) so I am playing with suspended probes.

It is a pain, my suggestion is to buy the enclosure and run a single UTH with installed fluorescent lighting inside and add a night led strip (I point the LED into the ceiling and hot glue over the sides to dim it it is seriously bright.) The leds don't produce much heat but the electronics inside do so it cools over night but not as much as you might think it has been working for me.

I get stable 90 24/7 inside the hot hide the cool hide has been 79-82 range the ambient air temps at 9am are about 79º at 12 they are about 82º at 3 they are about 85º they rarely get hotter than 85 The outside of the enclosure stays cool so the cool hide insulated the cool so it isn't becoming hotter it stays about the same. The temp hold that until the sun goes down then the house cools and air temps fall at 8pm they are often about 82º this is when the FL lamp goes out . The enclosure holds 80 until about 9 and drops a degree an hour until 11 or 12 when the led lighting takes over it keeps the temp about 78-9 the rest of the night. (combined with the insulation and hot side heater)


Your set up will not be mine but it is worth the try as it is likely you will have FL lighting anyway you can always buy a RHP or just heat the room up to 80 later but if the lighting works it is a cheap alternative if it does not then you have time to look to other options.