As between realism and idealism a change of belief has no significance at all. If all is phenomenon or idea then this applies doubly so for all the components of your realism, doubly because it is framed by your need to assert it. So if it is not your beliefs that have to change then it is your interpretation of them? No, what is called interpretation is only another operation performed between beliefs - they certainly apply to something, and they and what they apply to have the same metaphysical status, indifferently real or ideal. So if there is any difference, and there ought to be because experience, life itself s entirely different according to the decision made over this, then it can be no more than a matter of intonation, the movement of a comma, not even that.