The problem of entering the inner length of walls for multiple rooms have been mentioned many times in this forum and elsewhere. Sincerely, if there was a solution, I would be glad to program it, but I really don't see how I can anticipate whether a wall will be the last wall or not, and what angle it will make with next wall.
Think, rethink, rerethink about it and you'll see this problem brings you to a dead end. [:(]