What about something like
http://www.sportsmansguide.com/net/cb/cb.aspx?a=440496 or
http://www.sportsmansguide.com/net/cb/cb.aspx?a=418289 ?
Seems like one of these would be cheaper than the Fiamma room, serve the same purpose, and be less likely to damage the awning in wind or rain. I too, was looking at the Fiamma add-a-room, but many people cautioned against leaving the awning open if you are leaving for the day, in the event of winds or a lot of rain, which could damage the awning. Many recommended a standalone tent. But, these are angled just like the add-a-room and can be placed right against the TM, and even have an opening in the back for the doorway into the TM.
Any thoughts? I don't own one (I don't even own a TM...yet!) but they do look like they'd fit the bill with less cost and less risk?
Marc