I can't remember for sure, but I thought there might also be a fastener that is obscured by the door card. If the mirror isn't obviously free when you remove the fasteners behind the tweeter sail panel, your next step would be to investigate behind the door card. That's a bit of a pain, so I hope the sail panel does it. I just can't remember since I've had it all apart before. For sure though, the fasteners are definitely on the inside (passenger compartment) of the car. Be sure to disconnect the electrical connector that powers the mirror motor.