I downloaded and printed the Walthers ( N scale ) modulars templates and instructions. It seems quite easy to assemble that kind of structures. One thing that puzzles me is the height of the Large wall with the the railcar doorway ( 933-3282 part #20 ). That piece has a height of 40 mm while the height of a standard wall is about 29mm. So it's too high for a 1 story building and too small for a 2 stories building ( 58mm ). Could someone please explain how to make that specific wall fit in a modular building ? See the enclosed picture.