This is what I do, but not quite 80, 75 is fine for an ambient cool end temp, I won't let it go lower than that though.
Also if you put too many holes into the tub it will lower the tubs temperature too.
Below 75 could be an issue, but 75 for the rooms ambient is fineMy UTH set at 93 does not heat my ambient up more than .5 to 1 degree above room temperature. So If your house is cooled down to 75 or below you may have issues maintaining correct temperature.
A recipe for disaster...I have seen where some people have installed mettle mesh into the top of their tub lid and used heat lamps with a thermostat to control the ambient.