The C17 has its horizontal stabilizer mounted at the top of the vertical stabilizer, way above the plane of the wing
but most aircraft, including other large aircraft made by the same manufacturer (Boeing), mount their horizontal stabilizer on the tail of the fuselage, very close to the plane of the wing, for example the 767:
Placing the horizontal stabilizer so high requires the vertical stabilizer to be much stronger, adding weight and stress, so there must be a benefit/reason for designing the C17 like this.
What benefits/reasons are there for aircraft to have the horizontal stabilizer mounted this way?
