I feel like I need to correct my statement that the racks provide adequate stiffness to the 'standard' width frames from what I've seen.... it seems like the discussion is centering around the 'long' frames here. I haven't actually run across any 'long' frames myself..... yet.Those racks actually add a LOT of stiffness to the frames --- much more than the flimsy 'cabinets' do. Braces are always good, but I would say they are overkill with the racks --- you'd be better off using Z bars and trex if you put in the braces.