the waist is centered at {HEAD ~ an axial distance} from {TAIL ~ the front end} of the tip; and 
the waist is centered at { HEAD ~ an axial distance } from { TAIL ~ the front end } of the tip ; and
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH