I suppose Walpole can have his own interpretation (tradition); but he must use the doctrine of R.C. tradition and scripture to form his interpretation. He also must integrate supposed infallible tradition to his doctrine to guide his interpretation/tradition.Yes. Walpole cannot have an interpretation of his own in Scripture. His must be that of the Roman church.
If R.C. tradition is infallible, it would be advantageous in comparison to our system. The crux of the matter is whether R.C. tradition is infallible ... we obviously don't think so.