I agree with the comments above. With a Flow super, you shouldn’t need another super. When a frame is full, you just drain it, so there is no reason for the Flow super to ever get completely full, unless you are out of town for a long period.
The only time I have added a Langstroth medium (approx Ideal size) is if they are not capping the Flow super in very humid weather. The extra box on top can help with air flow and encourage them to cap the Flow super. Several other forum members have tried this and had success with it too. Otherwise, just the Flow super is plenty. 