Where to place dome for hot spot

I have a ceramic heat emitter For my 40 gallon tank however I have a four quadrant lid should I put the ceramic heat bulb on the backside or on the front side?

I prefer to pick the area with the most privacy and less activity around that spot of the cage.

For me and my setups that would be the back of the cage. I arbitrarily choose the right side unless there is an electrical outlet location problem.