Thanks a lot guys.

The shape of the resulting part is asymmetrical in real word so a simple projection did not do. Meanwhile I tried with drawing a freeform curve "through control points" with just surface snap on. Setting the points with care one gets a result with not too many control points and it will trim the basic shape of the shoe properly.

With your method I would have to make three parts and connect them. If the projected ends do not meet each other a 100% I would have quite a hard time adjusting since there are so many points. At least my first testing with this method was not that fun.

Michael, I had a look at the blue path and saw that the ends are not intersecting either. This is why I did not bother checking for that with the orange. But now I will do so...

Cheers
Rogurt

I took Danny's isect curves a step further and created a network patch surface that would yield the point structure of the "projection curve". This allows me to match both sides of the surface independently to recreate a curve iscet in a surface.....

Tried that also but it gave me quite a hard time on the forefoot area. I think I´ll stay with painting a new path directly onto the surface "through points" and "snap on surface".