stretching surface

 From:  Frenchy Pilou (PILOU)
4963.5 
Like this?
Here with Rail Revolve seems works, no ?
Call the Edit / "View Points" on the arc and move the control points for have a pendicular on each vertex so tangency!

Here on view top Profil is at the middle of the edge, you can also put it at the perpendicular from center to the edge.

EDITED: 27 Feb 2012 by PILOU