This is my third Osprey pack, so I thought I would have no problem with the Tempest 30. I have the Ariel 65 and the Tempest 16, and they have both been great packs for me. However, the Tempest 30 feels uncomfortable, due to the ventilation system, which I believe is an update. The back of my Ariel 65 and Tempest 16 looks like a washboard under the mesh. My new Tempest 30 has the accordion shape under the mesh, and it presses uncomfortably against my back. I've tried different adjustments with the pack but nothing has helped. Do you have any suggestions?