Setting Simulation Properties Under the Surfaces Tab Via Script

The following code is an old snippet that I've used in the past to set material properties. In this case, it never enters if( prop ), but works fine if I change "Dynamics Strength" to "Opacity Strength".

Anybody know if simulation properties under the surface tab need to be set a different way than normal material properties?

Thanks in advance if anybody knows.

- Greg

var nodes = Scene.getSelectedNodeList();
var n = nodes.length;

for( var i = 0; i < n; i++ )
{
    var obj = nodes[i].getObject();
    if( obj )
    {
        var nShapes = obj.getNumShapes();
        for( var j = 0; j < nShapes; j++ )
        {
            var shape = obj.getShape( j );
            var nMats = shape.getNumMaterials();
            for( k = 0; k < nMats; k++ )
            {
                var mat = shape.getMaterial( k );
                if (mat.getLabel()=="1")
                {
                    var prop = mat.findPropertyByLabel( "Dynamics Strength" );
                    if( prop )
                    {
                        prop.setValue( .99 );
                    }
                }
            }
        }
    }
}