Hi, I don't know how did you set up the view, but you should be able to change the cut plane using a 3d cutaway.
The way I set up those plans is:
Open a regular 3d View without camera.
Cut the plan to the desire height.
Change the view from Perspective to Axonometric.
Use look to perpendicular of clicked surface, and click in the floor slab, that will make the view from the top.
And finally save the view with the settings.
With this method you can change the height of the cut plane any time you want and just re save the view.