model.setValueAt is out by 1 position after upgrading to Ready! API

I've just upgraded from SoapUI Pro to Ready! API. My scripts use extensive use of model.setValueAt() to populate datasource grids e.g. model.setValueAt(tempPackID,rownum,0). The problem is that Ready! API has an extra column at the start of the grid so that now the column positions in model.setValueAt are all out by one. Is there any easy way to change this?

Thanks.