[PyQt] QTreeView Drop Target: Between Rows, Column 1

[Doogster]

How do I set the drop target in my QTreeView to be between any row in Column 1?

To set the drop target to be between rows, I have flags return
ItemIsDropEnabled if the index is invalid. However, an invalid index
has both the row and column set to -1. That prevents me from narrowing
the drop target down the spaces between rows in the first column.