modeling taper round wall from pointcloud

[mgebel]

Hi.

 

I've got a head scratcher:

 

I have a laser scan of an existing stair rail, and I want to model closely what is there, so a new rail cap can be fabricated to fit. I can easily trace the edges of the wall in plan view, but when it comes to creating the sweep, I'm stuck. The highlighted object is a nurbs curve, which is reasonably close to the top edge of the existing wall, but doesn't follow the surface of the extrude, as it was drawn separately.

 

The round wall tool works, sort of. If one were able to convert a polyline into a round wall object, then I could probably use the sweep degree to get reasonably close, but because the existing wall was handmade, it will never be exact.

 

I'm imagining there is a way to project the nurbs curve onto the solid to trim it, but I'm not familiar enough with these operations to figure it out. If anyone can point me towards a tool or a technique for this type of geometry, I would appreciate it immensely!