Find ExtrudeEdgesByRails [or the whole EEby... tools zipped].
I'd make it in two mirrored halves as it looks symmetrical.
Use 'weld.rb' to make part of the outline a single 'curve'.
Repeat for the rest of the outline.
Now you have two curves that can become 'rails'.
Draw a third curve (perhaps a very flat arc) to for a profile.
Use EEbyRails picking them as prompted [repeat pick on profile unless you want it to end slightly differently in which case make another curve/melding-profile... It should make a mesh of the surface. Then process it as needed - here's a visual clue... I know it's not the same shape but I did it as quick example for you...Untitled.png
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