A follow-up.
The Kampa awning I used was a single airbeam porch model, which uses the tension in the front guys to tension the awning roof. If the awning was fixed directly to the caravan rail there would be no problem, but because I had it attached to the Fiamma the tension started to pull the Fiamma awning out. The side opposite the winding handle was the worst, pulling the Fiamma about six inches out from its casing and needing manual assistance to wind it back in.
I think a poled awning would probably work better than an airbeam because the whole weight of the airbeam awning is suspended from the closed Fiamma, which isn't really designed for it. Something I hadn't really considered when I bought the airbeam.
Have now given up with the Kampa airbeam and purchased a Fiamma Privacy Room for next year, on the basis that the privacy room and the Fiamma awning are designed to work together.