I have a solution for the realy ugly Chewbacca face.. a simple replacement of 1 brick in instruction #517 gives him the look everyone is looking for...
Just replace the 2x1 plate by a 2x1 plate with rail attached (lego part 32028)
The only problem is ... the brick which replaces the original...doesn't exist in the wanted form... however it's a simple altering of a black brick (or a white version)
The thing is...the rail on the brick has to be become white and the long side on the other end has to be become (or stay) black... so either you paint the rail white (i did), or the other side of the brick black.
By replacing this part, Chewbacca gets a full teeth in his upper jaw, which gives him a friendlier and more correct look