The 49 l rackpack is 3 inches wider than the 31 l. And the 70 l panniers are 4 inches (each) wider than the 40 l.

By looking at the various photos (thanks all), I think I will be too wide to my taste. And I am sure that I will packed the free space under the rackpack and maybe exceed the limit of my rack.

I think I should keep my 40 l panniers, buy the 31 l rackpack and put some stuff on my front rack (support 18 kg). Also, I think I should reduce my "essential" stuff ! Decisions, decisions