IO540
I am not sure that is correct.
Rules 24 and 27 specify the minimum visibility and separation from cloud in terms of horizontal and vertical distance required to permit VFR operations.
I thought the rules also specify at or below 3,000 feet in sight of the surface.
If that is so you might well be in VMC above a layer but depending on your separation or altitude never the less required to declare IFR.
800 feet above the base and you are IFR.