I like to pat myself on the back that my World of Cinder is pretty dang expansive, but lately I've been wondering if maybe a Traveller subsector map is less than totally ideal for a mostly-D&D setting. Crazy, I know. From the point of view of the average PC locating the Wilderlands (for instance) on another planet isn't that different from placing it in another dimension. A more practical arrangement might be something along these lines:
Finding Carcosa just across the mountains from Aragorn's homeland might make some folks' head a splode, but it pretty much sums up how I like my D&D.