In terms of temps, that doesnt sound too bad. You want to be careful though, because if your cold side is 75 during the day, its most likely going to drop a few degrees at night, and I heard anything under 75 is unhealthy for balls.

You should also have two identical hides, one on the cold side and one on the warm side. I have a 20 gal right now, and I have no problem fitting two big hides on either side and a water bowl for her in the middle. Soon to be upgraded tho