If it really has 2 independent 12V rails, then no it's not a good idea because current would still flow between them any time they're not exactly matching each others voltage.
I have broken PSUs and spare controller chips. I'd like to see how much you can setup up the controller chip to output different voltages. But most of the output caps would need changing as they are only 10 and 16V rated. The output controller and all the feedback circuitry and over/under voltage and current protections, would have to be disabled or really really modified.
I don't really know how flexible the flyback transformers are in there operating frequency.
But since I have both types of controller chips I should strip down 1 PSU to the basics and use my own chips and controller/feedback circuits and see if these can run as a variable bench SPMS