euroherbal said:

Look closely, my friends: see how the bottom wall is at the beginning of a ramp? :) That's why we don't see the chamber's rim in the next shot: it's below eye level.

Mistery solved!!! :)

Not sure what you mean here exactly euroherbal. But I've just noticed in the 3 top shots I showed on the previous page, that it looks like the whole of the bottom step of the 'chamber' prop is itself 'raised up' a little with an angled bottom section. At the end of the day, the relative distance and height of the props to each other are a little easier to judge if you rewatch the footage a little.

I'll happily accept whatever adywan's take on it is at the end of the day, though. :)