How to remodel 3D mesh plates with deflection (with model and Pix)

Hello all,

I have some surfaces with changing thickness along the geometry., meaning that my shape is kind of camberic and have slope towards both downwards and sides. I need to extract the outer faces or get the midsurface from this plate that I turned into nurbs from mesh. Since the plate was mesh, it has no clear face to be remodeled. I can’t succesfully use extrudecurve and intersection commands here. I wonder if I can remodel it properly with clean surfaces. However, trim and boolean commands didn’t help.

Hope someone would help and thanks a lot.

please see thr pictufres and view model below.

meshsehim.3dm (2.6 MB)

Might help to post the original mesh - it looks cleaner than the nurbs model.