The SP_DisableFlipText property disables the flip text behavior of the Smart Label when set to True. The display name is Disable Flip Text.
The text box within the label flips when it is rotated by an amount more than 90 degrees or less than or equal to 270 degrees. This is done so that the text can be read bottom to top. When the Disable Flip Text property is set to True, it disables that behavior.
In Catalog Manager, this property can be set so that text can be displayed upside-down if desired.