If you are using 50" paper then you can either think "keep it flat" and use a vacuum easel, or think "lots of depth of focus" and use sticky tape / magnets.
(Meaning flatness isn't a huge problem, though the middle of the roll is more curly than the outside...).
Martin, that's equally for MGIV matt and MGIVWT semi-matt? Do they behave the same? I manage to flatten 24x30" Emaks (graded glossy FB) cut from 42" roll under RBB 20x24" easel relatively well. Once it lands in the tray, it's soaked and flat within seconds. Drying it flat isn't all that easy, whereas WT semi-matt is a joy in this regard.
For the drying I'd tape it to a large window, unless you have a dry mounter for heating the print in sections until it's dry. My post above was based on memories of making large prints twenty years ago [EDIT: that was rolls of either Polycontrast RC or Ilford MG RC]. Developing them was by scrolling them through deep trays/troughs. Regarding current paper rolls and their curling during drying, unfortunately I can't really help you.