Hello - I think I’d at least try making the side panel as all one surface - at least there at the rear where you have is as three - and trim that sharpish corner shape at the trailing edge rather than try to build the surface edge to edge.
As is, with the three surface layout, I’d do this:
Make the transition surface a blend surface with History.
Make some vertical lines in Front and project these onto the blend, with History, BringToFront and CurvatureGraph
You can see the anomalies more easily, along with Zebra of course.
I would also simplify the lower surface to degree 3 in U - just fewer points to manage.
Then, with MoveUVN and very small inncrements, or DragMode > ControlPolygon and DragStrength set low (25% say) make small adjustments to the upper and lower surface points and watch how they affect the curvature graph on the section lines - you want these graphs to be all ‘positive’ (not switching sides) and somewhat similar and progessive in shape. I tihnk you’ll have to accept that the outer edges where you already have some transition surfaces in place - maybe prematurely - will change slightly.
I moved some of the interior points in the upper surface along their control polygons outward, radially , a bit as well as normal.
mcNeelSample_Somewhat.3dm (185.8 KB)