That was news to me, everything I read and used were marked double din.
You are into this much more than I am, so I bow to your superior knowledge.
I checked and can't find anything listed as double din and a half, but then leave it to Ford to build a non standard item.
For reference, the two head units I have here on the desk are 2004 6 changer and 2006 MP3 single. The bodies of both are 4.5 inches thick. So that exceeds the 'standard' double din by 1/2 an inch. I know you can mount two single din units and they just barely slip in, but the faceplate on each of these OEM units has a big rim around them. If you had a 5 inch unit I don't think it would fit. Not that I've ever seen a five inch thick headunit. That would be a big honking head unit.
Chris