That's interesting to hear. My experience is that I've generally slept better on the Mark 5s than I did on the Mark 3s. But it's difficult to know how much of that is due to external factors (perhaps I've been more tired? perhaps I've found the perfect quantity of single malt to consume in the lounge car?).But, particularly when travelling south, many items will be "off" in my experience
Now I've found this thread I've moved this post here, from the new thread I started.
Having used both the Night Riviera and the Caledonian Sleeper within the past two weeks I feel in a position to compare them.
I slept slightly better in the Mark 3s than the Mark 5s. The ride seemed better - whether this is due to the suspension or Brunel's civil engineering prowess I don't know, but I woke up several times on the Scottish trip but slept until after 6 on the Riviera.
Comparing CS Mk 3 vs Mk 5, I also think the Waverley shunt is now much smoother and therefore less likely to disrupt sleep especially northbound.