What would the be actual dimensions of a 1/6 Falcon?
The original fiming model from ANH was 1/24 scale to match the x-wing and Tie models that were also 1/24 scale. The filming model which is often called the 5ft Falcon was actually 5.67 feet long. 5.67ft x 4 and you would have a 1/6 scale falcon at 22.68 ft. long based on the Studio miniature from ANH.
As for the measurements HT used depends on what they are basing their scale on...and how long HT thinks a full sized Falcon would be. Depending on source you can get a length for the full sized Falcon as anything between 80ft and 152ft many people seem to agree that Robert Brown's calculations as documented on his Ship of Riddles site are about right, certainly that's what the Full Scale Falcon guys are working to. That would give an overall length of 114ft or 34.74m, divde that measurement by 6 and you would get 19ft in length for a 1/6 Falcon.
So its all really a matter of opinion...The Falcon has about 3 different sizes:
The 5ft model was the first thing ever built. It has 1:24 model seats inside. The ILM crew built all the ships that were dogfighting in ANH to that same 1:24 scale in case it proved useful. This points to a monstrously big 136ft full size ship.
The soundstage sets were extrapolated off the 5ft model. They were never even ballpark close to fitting each other or the ILM models. The interior sets suggest a 114ft Falcon. The cockpit got 18" deeper (front to back) for ESB & ROTJ to give the actors more room inside.
The 1:1 exterior shells (just the right side for ANH, and the whole ship for ESB) were radically undersized to fit on the soundstages. They were only 82ft long. You can visibly see the cockpit is too small (compared to the interior scenes) when they are walking around underneath it.
The closest thing to an official size, as of 2015, is the 114ft interior size. For Ep#7 they have built the 1:1 scale exterior shell that big for the first time.
