I am very glad to read that the "should be done" is ... already done.
But, as I said, I used to print on another 3D printer which is using proprietary software and I can insure you that the printing have "exactly" the same dimensions, inner or outer side (of course, in relation to the precision of the machine). This firm have been manufacturing cnc machine since a long time and they came to the 3D printing market.
When I look to my new printing using Cura comparing to the others, the internal dimensions of horizontal holes look like so "rought" that I cannot beleive that the inner side is calculated correctly.
That's why I really would like to understand why there are so much differences.
Is there any parameter I can change to have it better ?