What is the best way to smooth these curves?

I am modeling a spiral staircase, and these will be the solid steel railings on each side. As you can see, when the railings get to the top, they level off and go straight. I’m trying to figure out what is the best way to get the smoothest transition from the spiral part of the staircase to the straight part.

The curves need to lie on the surfaces so they will create a cleaner geometry. I have tried to blend the curves as the point where they level off and then pull them to the surface. This works to a degree, but I would like to see if there may be a better method.

2019.05.17_mcneel_forum.gh (25.3 KB)

Blend seems a good solution to me as it allows a smooth transition (curvature continuity)

2019.05.17_mcneel_forum_LD.gh (13.9 KB)