Sweep 2 rails -> surface is over the rail

During wing design I’ve faced strange situation.
If sweep over 2 rails is done between large and very small profile, then final edge is over the rail up to ~ 0,1mm.
If the difference (rail curve?) is reduced the final edge is closer to the rail but not perfectly.
This can be easy seen on the leading edge of the wing.
Trailing edge is ok.
This phenomena is visible after .stl generation - so I guaes is not visualization point.
Is there any way to force the Rhino to keep strictly the rails?
I tried in options to find any parameter, but is there any?

issue_sweep_2_rails.3dm (194.6 KB)

Hi Codi - on the left hand set of curves the smaller cross-section curve does not intersect the curved rail, quite.issue_sweep_2_rails_PG.3dm (126.1 KB)


Dear pascal.

I don’t know how I hooked up the profile to the rail previously…
Now I did it with “intersection object snap” and it works perfectly!
Second time to you: