Thought it would be a challenge and a good tutorial for myself not perfect but...

Thanks for the method Michael. After forming the surface like in your last step I did an offset, then loft between the cutouts then a couple of trim sheets for the sides.
I have a question, is it possible to have like a 'solid offset' I tried extrude but it deforms as it goes around the curvature of the sheet, just a thought I had as I was doing the surface offset.

Cheers
Danny