Here is a try, using png image captured from STL viewer "GLC_Player."
The view is sized to approximate the same size as the .3dm
For the Flow target curve, the center bent curve was made using Blend, with the green helper lines.

Created center line for the .3dm to use for the flow baseline.
The lengths of the two curve lines were not quite the same. Could have used some kind of scaling perhaps.
Used the stretch checkbox in flow.
Used UnwrapCurve for lengths.

Your .3dm appears to be thicker than the .stl.