Someone who knows a lot more about this than I explained to me that the 'demonstrated crosswind component' is a purely structural limit, not an aerodynamic limit at all. . .. .It means that the landing gear will stay on in an uncorrected crosswind landing.. .. .One night, on take-off from Biggin RWY21, I found another limit in a 45 knot headwind: my eyeballs were bouncing so much it was impossible to read the instruments, this was in a cabin class twin near gross.