I just ordered my second boaphile 421 coupe. I absolutely love them!
I wouldnt worry about it hurting your cage. I do however highly recommend boaphiles heating systems. They use low wattage heat tape, so even full force, they will not get hot enough to burn your snake. Now control that with a thermostat or a rheostat and you have double protection from overheating.
I think it is well worth it to get boaphiles heat tape.
Good Luck!