Originally Posted by Jim Kukula

Ah, I can see from the picture, you have the upper attachments fastened to the horizontal supports of the rack. That is surely much more secure and less liable to shifting. It puts the bag higher too, which helps avoid heel strikes.

Another possibility would be to loop one attachment to a horizontal rack support and another to a vertical support, to angle the bag which should create some heel room.

Our teenager has a Topeak rack bag that slides onto the rack, and I didn't want the QL3 system to interfere with that. Probably he won't need to use both bags at the same time but it would be nice for him to be able to pick, e.g. Office Bag for going to class, rack bag for weekend exploration.