I'm working through the same issue . . . but find no one is giving me a recipe for calculating how much fabric to buy. I think you're going to have to measure and fake it.
Drapes generally require 1.5 to 2 times the length of the window track. You can easily measure the height. Your videos . . . or some written material . . . should give you an indication of how much to allow for hems, etc.
It would be very hard for anyone to give numbers because it depends so greatly on how you gather your drapes, how wide the fabric is, and what the measurements are on your specific Airstream. Eg, in some cases a wide fabric might cut in half to make two window coverings.