I wanted to begin with the shuttle because it's one of the most consistent scale establishment throughout the trilogy IMHO, because it will serve me to make my point later and because it illustrates my way of analyzing scales in a positive way (I think).
So for this one I think every one is pretty much ok with a 20 m long Tydirium…
The next ship I'd like to analyze is the Tantive IV "Blockade runner":
This one is not as easy as the Tydirium, as the only good comparison we have is precisely the ISD so…
But at least we can say that a mile long ISD would make a 150 m Tantive, and Ady's 2 mile ISD would make's it 300 m
(is that what you meant Ady? I postulated 3 times the 1 mile ISD before, but I think I was wrong, I'll come back to that later)
So the best we can do for now is make assumptions with the little we got from the movies and see later how it holds in the "big picture" (at the conclusion of my 1 mile ISD plea).
Ady you said that "the so called official scales of that ship are still based on the original scaling" when the Tantive was meant to be the falcon, right? I assume you were talking about this rough sketch made by Joe Johnston?:
Actually this was not what I was talking about, it looks like 50 m here, and, as you said, that wouldn't be consistent with the interiors set we see in ANH. The official size at SW.com is 150 m, but that's not because it's official that I made a 150 m Tantive in my scale chart. Let me explain…
Here are some scenes from ROTJ (as everything is moving you may want to watch the actual DVD for a better feel):
both scenes seems more or less continuous to each other but it's verry hard to guess a size from that (especially since the Falcon size brings its own debate). So let's say the Tantive here is way bigger than the Falcon…
There's another one:
this one is odd regarding the previous two, it feels to be about the size of the Falcon according to this other shot from TESB:
So as this particular scene from ROTJ is off regarding the whole saga, I'd say let's discard it…
To conclude, even though it's only an assumption, I like the 150 m Blockade Runner because:
A. It makes the OT shots consistent with this shot of the Tantive IV in TROTS:
the humans inside the cockpit are making a good 150 m consistency too:
B. At that length the interiors set could fit inside, as this nice reconstitution proposes:
C. It makes sense for me in the whole saga, but I'll come to that later…
you can see below a 150 m Tantive as portrayed above:
What do you think guys?