I have a spherical-like object whose thickness is 1.6 mm. There is a section of the surface that is to be only 0.8 mm thick. So I changed the thickness of the entire object to 0.8 mm, then selected the faces that define that special region, then pressed P to separate it from the rest of the object, then changed the entire object's thickness back to 1.6 mm. So now that special region is 0.8 mm as desired. The problem now is the gap between that region and the rest of the surface caused by the separation. I want to close that gap so that from the outside, the surface looks like a single surface and no one can tell where the 0.8 mm thick region is. What is the most precise way to do this?
I tried moving the edges and vertices of the region so that it intersects with the original surface, but the intersection is not clean (see below). How to do it perfectly so that it looks like the original surface from the outside?