I have a 40gal tank in a room that is 66-68 on average. I use a uth and 100 watt che on the warm side, and a 60 watt bulb for the cool side. I have a mostly covered screen top with foil tape.

With the right size bulb you should be able to get the right temps. Just be sure the bulb does not create a hotspot that is way to warm. I use lamp stands to give me the ability to raise and lower the lamp to get the perfect heat coverage. They will also extend the life of the heaters because you are not bouncing them around moving them from the top every time you enter the tank.