I've seen two T5500 with case awnings like the Fiamma (one was a Fiamma F45, the other one I'm not sure, but very similar at least).
Instead of using attachment brackets like Fiammas usually have, the awnings I've seen were mounted on a 2" aluminium angle that ran along the original awning track (probably screwed or bolted to it I guess). This spread the weight
and load along the entire edge of the roof instead of only 2 or 3 brackets, and raised the awning case a bit, giving more clearance with the top of the door.
On the 5500 the top of the door is very close to the rounded edge of the roof, there is only like a couple of inches between the top of the door and the awning track.
I would have to look at them again before I decide on how exactly to mount one on mine.
Does someone knows if Fiamma USA is back in business since last years' events?