This thread my be helpful, but unfortunately the hatch design has a few issues as you have discovered. When it is wet I just open the hatch very slightly until the water drains away. I am also very happy with the prop rod solution. It is impossible to make it hands free like a modern car.
http://forums.pelicanparts.com/porsche-924-944-968-technical-forum/1004864-decklid-glass-separating-frame.html#post10173784