Heat mats are hot enough in fact they can be too hot, you will need to use it with a thermostat or a rheostat.

And Im sorry I didnt realize that the measurements of those enclosures were in CM not IN... The large will be fine... However for half the cost you can buy a plastic tub with a lid on it and it will work great... Just make sure you get hides that are nice and tight for the snake to fit into..