Hmmm… so extruding or extrude/scale along normals isn’t working for me. And adding shrink wrap to the vertex group with an offset doesn’t bring them back in line.
I want the extrude at 90 degrees ie all the extruded edges on the same z height as the inner ones they are being extruded from

I tried selecting the edge loops and snapping on Z to the inner vertex but the Z height slopes downwards from left to right so that doesn’t work

Then tried an extrusion, Scale with shift Z, and a shrinkwrap with offset to bring back and even width but it’s still wonky


It feels like all these issues must come back to my original mesh cos this doesn’t feel like it should be this hard. Starting again!