Got my speakers installed yesterday. Just wanted to add that I did not need to remove the rear seat belt attachment to gain access to the rear speakers. The bottom panel will come off but I would recommend removing the rear door sill first, then pull back the door seal just enough to clear the bottom rear plastic panel, then gingerly pull the bottom rear panel out, starting from the top. You will not be able to fully take out that bottom panel, you are just looking to pull it away enough to gain access to the speaker.

And BTW, here is a cell phone pic of the new vs Ford OEM speaker (on right). Everyone is right, the OEM speaker is pathetic and when listened to directly, is very muddy sounding. The sound out of the new speakers has MUCH MORE clarity.