You can create some "fairly" exact cap shapes with a method easy like this. (if you want to be "Precision", then you may have to practice a bit)

With this, I can get the same verticle cross sections as in your first posted filem which will produce a fairly close result.

Revolve a curve like this, being sure to create a point for each cross section you will need. Call this the resolution of your surface.



Then you'll get this result where you can delete the bottom surface and turn on points.



Each level of points can be moved up and down to match your cross section curves, and contain enough points to approxamate the shape that exists there. this will produce theis type of shape with very smooth transitions and curvature as you are looking for.



Sub-d NURBS.

[EDIT] Sorry, Seems I thought I was replying to this thread and shape:

http://moi3d.com/forum/index.php?webtag=MOI&msg=2909.1

But it may apply here also! [EDIT]