You know the ones: Gregory Z55, Osprey Atmos, Deuter, etc. The backs of these packs have a mesh panel that in theory keeps the back cooler and drier.

Do you think they work?

The only drawback I know of is that it the design can infringe on the interior of the pack. The curve of the design eats into the space and makes packing harder.

Do you think that the design does indeed make your back cooler?