Yep, no belly heat needed if your ambient temp is up to par. I personally keep my enclosures at 83.5 during the day and then do a night drop of 80 at night. The night drop isn't something that is necessary either. I'm just experimenting with night drops to see if it makes a difference or not.
I would mount the RHP panel either on one side or the other. That way you're creating a temperature gradient for the snake. A 80 watt RHP should be great for a T8.