Pics of the underside of the hatch? I have seen many that have rust through on the underside at the bottom corners.
If the only rust is the hatch, find a rust free one and swap it. Far better than trying to repair the rust through you have there. Trust me, that rust goes right through the metal and if you start grinding, you will end up with a hole before you get clean metal. Even repaired, it is more likely to rust than if you find a rust free hatch. They should not be hard to find in Cali. Save the back glass from your old hatch as it is hard to find.
If the only rust is the hatch, find a rust free one and swap it. Far better than trying to repair the rust through you have there. Trust me, that rust goes right through the metal and if you start grinding, you will end up with a hole before you get clean metal. Even repaired, it is more likely to rust than if you find a rust free hatch. They should not be hard to find in Cali. Save the back glass from your old hatch as it is hard to find.
