I uploaded you skp file an open it
Took line tool closed the 4 areas
check dimension
[image: njNU_pic_0026.jpg]
resized top 3 areas
pushpulled the botttom one
Context Intersect with selection
[image: tbkM_pic_0027.jpg]
Trim and remeasured
Tested the volume and smoothed the edges
Tranpanency mode
[image: 2Sze_pic_0028.jpg]
My error was inside material need deleted before runing the test
If makring a ring skin then
10) After push-pull smooth the pull volume
11) Context Intersect with selection
12) Make group then explode, use the erase on back edges
[image: YVYQ_pic_0035.jpg]
13) Done
[image: zdBk_pic_0036.jpg]
I hope this may help?