Unsolved QML TreeView: rowDelegate height variable with model index.

[Cesario]

Is there any way to define the row delegate height based on any model data ?
I mean, something
rowDelegate : Rectangle {
height : model.itemHeight
}
... where model.itemHeight is a function of the model index.

I did some test: it seems to work, but if you delete some index in the model delegate you could end up with a crush : (

Thanks a lot for any suggestions.