i've found that the best compromise with the arca ground glass N is with the rodenstock 6X loupe.
with a 6x9 screen you can preview a stitching...
By the way, Kapture Group have the best support possible... Keith Hugues is a fantastic person to deal with !
The Kapture Group sliding back is really small and convenient, it packs nicely compare to the rotaslide.
But with an RM3D, you don't have the choice, you have to go with the rotaslide because of registration.