Pete, Jim, thanks for the pictures.
I've come full circle back to thinking about saddle bags because they offer the possibility of carrying capacity without racks. They seem to offer the tantalising combination of volume, robustness, simplicity and relatively light weight. I was hoping the springs on the flyer would help support the bag better than a B17 would. I think all bike luggage frets against something somewhere.
When I read about bikepacking elsewhere I feel sure the saddle bag is about to get reinvented soon.
Thanks
Ian