I’m about to attach my guardian hive reducers to my flow hive brood box. The hurdle I was concerned with was matching the opening of the guardian with the opening of the brood box in line with or at the entrance point of the metal screen.
I created a frame for the guardian and plan to attach that to the outside of the brood box. So the guardian is actually inclosed with in the attached frame around the top and sides.
Your solution I just found after making my set up.
Yours looks cleaner. How’s it working for you