The fabric is soft and flexible so that it will drape well on a long, slender frame. Note that these shirts are intentionally over-sized slightly to account for shrinking when washed.
Machine wash cold and tumble dry low to minimize shrinking
The chest measurement is straight across the front of the chest from armpit to armpit. The length measurement is the full length from top to bottom. The sleeve measurement is from middle of collar to end of sleeve like traditional dress shirt dimensions.