A 50 gallon is way to big for a ball python. They dont like open spaces. If you intend to use it anyways fill it with giant plastic plants from a hobby shop and some large branches.
The under floor heating is enough if you cover the sides and back with some kind of insulation. Like styrofoam or thick cardboard. You will also need to cover most of the top to keep the humidity in. Put in several hides and a good sized water bowl.
Dont use a heat light or your snake will have a hard time shedding.