Hello,
the best way is to put your locators in the monitor and also around it, in the table or in the top of a book for example, put beside the monitor.
If there is not enough texture in the monitor, you can help drawing a cross in it.
Remember that IM prefers to have the points NOT all in the same plane or too much grouped. Always, prefer to define the more possible volume with your locators.
The calibration will be easier like this.
If you still have problem you can send your images to support@realviz.com.
thanks.