I dont know... It's nice and all but you really need to be sure everything in her area is proper. Higher humidity than usual, make sure she doesnt lay on top of the heat tape, etc (this is assuming the same general rules apply for maternal incubation as do for artificial incubation). I read somewhere that balls are one of the few snakes capable of altering their body heat and the reason being so that females can have more control over the temp of their eggs.
Personally I'd rather incubate in an incubator, the only real flaw I see to that method (assuming nothing goes wrong) is that you could be doing psychological damage to the female.