How to control elevation of geoshow() contour lines

In our application we need to sometimes plot contour lines from geoshow() on top of other geoshow() surface plots. In order to make them visible we need to raise them in Z by a few units. We can find the ZData for the contour lines but when we try to change it we get this error message   "Insufficient number of outputs from function on right hand side of equal sign to satisfy overloaded assignment."   The geoshow() call we're using is this.   A = geoshow(latMat2, lonMat2, newRain2, 'DisplayType', 'contour', 'linewidth', 1.0); Once above command is executed, we can see the ZData (all zeros) with this A.Children(:).ZData We try to swap in new ZData values with this A.Children(:).ZData = 8; and get the above referenced error message.     Obviously we're doing something wrong, but don't know what it is.