Though not a complete container change [with SLF] Armstrong Whitworth had a proposal for a rapid change for the Argosy of a complete cabin using the on board "Rollermat system it was proposed to B.E.A. but was never got passed the prototype stage . I saw it on the prototype airplane on a visit to L.H.R in the late 50s very early 60s before we took delivery of our small fleet later.