Map to Srf vs. Flow Along Srf

Hi all,

I am trying to get GH to simulate the Flow Along Srf command.  The base surface is not straight-edged, so (I think) I can't use the Surface Morph component, which asks for a reference box.

So, I'm using Map Curve to Surface, which works pretty well.  Unfortunately, there seems to be some sort of tolerance issue, and I am getting some distortion.  (See Attached)  Is there some way to reduce/eliminate this?  I am so close to finishing this project, and this is the final little detail!

Thanks,

dh