Thanks everyone, I have had my Camper Longflap (nearly right Nate!) since mid August and have put around 1000 miles on it and the straps are looking crushed where they loop through the saddle loops.
I do carry enough food for a small army (potatoes, tins of beans, bread), clothes etc, so I have taken your advice and ordered a bag support. I must say that the bag just performs, ease of use, weatherproof, huge amount of space, and along with my B17 look forward to MANY years of use -I love it.

Thanks again, Dave