The head pipe has a supporting surface portion corresponding to {HEAD ~ the surface} of {TAIL ~ the aforementioned warped intermediate portion} 
of
The head pipe has a supporting surface portion corresponding to { HEAD ~ the surface } of { TAIL ~ the aforementioned warped intermediate portion }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL