Before you switch altitudes you should also let the controller know your intentions. If you’re doing maneuvers you can choose a segment of airspace between two altitudes, which you would refer to as a block. But regardless of what altitude or altitudes you choose, you need to comply with the controller’s instructions if the altitudes you’ve selected don’t work for him or her. While VFR-on-top, you must “comply with instrument flight rules that are applicable to this flight; i.e., minimum IFR altitudes, position reporting, radio communications, course to be flown, adherence to ATC clearance, etc.,” according to the Aeronautical Information Manual. You also have VFR rules to contend with. You need to maintain separation from other airplanes and appropriate separation from clouds, based on the airspace you’re flying in.