Pilou,
My apologies,
The reversed faces problem seems to disappear as soon as the combined face is covered in a material. Not sure if this revered face problem will cause any other underlying issues, but visually it now looks fine

Thanks Pilou,
Have managed to get a similar result of a smooth transition without distorted edges. Not sure what I was doing wrong in the first place, but now I have the problem of mixed - now "welded"faces (for lack of a better word) that I cannot seems to reverse. In your gif, the face on the top left is reversed. Have you managed to find a solution for that?

Hi guys,
I'm trying to design a guitar with a curved back.
I need to be able to "inflate" the back without distorting the edges.
Have tried the sandbox native tool, but there does not seem to be a way to deselect the edges.
Have also tried Curviloft and soap bubble plugins. Maybe there is a way, but haven't been able to get an acceptable result with those so far.