Honestly when it comes to questions on mutliple snakes being housed together I am not going to be any help as I do not have a clue how this affects the snakes......
If they are both about the same size I do not see what the problem would be in going and getting a cheap 10 gallon tank and another UTH for the second snake.....I know at the reptile store I go to I can get a 10 gallon for $10 and a UTH for a 10 for under $20....$30 seems cheap to me compared to the possibilities of injury to one or both snakes requiring vet attention or having one of the animals killed.