Hi,
The picture you posted might look a bit convoluted but it looks to me like it is really a series of lines and curves.
I would select the biggest part that is flat and use that as the surface and create a sketch and then using the known
measurements (I am assuming that if you designed it you know stuff like the radius of the curve at the bottom laces)
and just draw a single line (in 3D) straight down the middle of the flat part. You might have to change where two edges
meet in an angle to a curve but the line itself looks fairly straight forward in the picture. The line would go straight
down the middle where your red arrows are.
Once you have a line that is in the right place then simply use Pipe and it is there. I don't think Sweep is working
because there are angles instead of curves. Maybe it would work if you changed those angles to tangential curves
instead.
Cheers
Andrew