hey guys,
i think the black strap you speak of is actually supposed to be formed into a small "tophat" shape that the "brim" gets placed under the 2 straps and the "hat" portion between the straps and projects downward to touch the bypass bottom. this keeps the engine centered especially when there is a hard landing.
picture engine held on the sides by the 2 tabs, and being held up by the tophat which is between the lower turbine body and the bottom of the bypass.

Kirk