The EN World kitten
The red boxed set was the second of Ravenloft's 2E incarnations (the first being the original Forbidden Lore boxed set, whereas Domains of Dread was the third). The poster maps in the red boxed set used different scales for the various islands of terror than they did for the Core. Har'Akir, surprisingly, looks like it was at its smallest in that set:I'll take your word on that. I have the red box (which I think is the revised version from 2E), and its scale is 1 inch = 100 miles.
The map in that one shows the Sleeping Beast mountains as about 150 miles and Falkovnia being 350 miles across (hardly able to be crossed within a day).