Doh!
I just realized that my old OBJexporter has greater precision !
[numbers are in " but units are set in header] e.g.
vn 0.686281746817 -0.727335798641 0
Here’s a link to download it:
When its RBZ is installed it appears in the File menu and because it’s old it’s not signed - but will work in v2020 with Extension Manager > Extension Loading Policy set to Unrestricted…
If you don’t have a membership, you can get a free one at SketchUcation - as you might desire…