Feedback master - how to make them all the same?

Hi There, I am trying to clean up a quiz that is actually a compilation of a bunch of individual quiz banks. There were literally dozens of different and unique slide masters being used. I managed to get all the slides using our corporate approved theme, and I deleted from the Slide Master all of the slide designs that are no longer being used, but the feedback masters are still a mess. If I go to View -> Feedback Master, there are 27 different designs used. All of them are being used on at least one slide. I don't see any way to get them all on the same format. For example, in the Design ribbon, you can right-click a slide and select "apply to all", and magically all of your slides look the same. This somehow doesn't exist for the feedback layers... or does it, and I don't know where to find it...?