The removable bar does allow (help) the sidescreens fit on the underside of the rack.
Do you have a trad with a spare wheel ? The sidescreen storage does lift the rack a few inches higher, which causes a bit more restriction to the rear view once the suitcase is fitted. I removed mine and fitted a rack without the side screen storage.
However, as I saw marked in the rear view mirror of a D Type Jaguar, ' Warning - vehicles in the rear view mirror no longer matter'