Happy to hear that you solved your immediate problem! It is always a nice feeling when we get things working the way we want and when we want.
I downloaded your one example grib file. Thanks for sharing it. Looks like it uses a negative y-Delta. I encountered that situation once before with a different grib file. I will investigate further once I return to work.
In addition, I will add new "Map File(s)..." functionality to map a set of grib files to a BINARY multi-frame T3 2D Scalar mesh (*.ts3). This will "get my feet wet" with this new feature. And then, once that's completed and made available in a new alpha version, I'll look at more directly mapping onto a *.slf file. Baby steps
If you (or anyone else) have any requests related to this new functionality, please feel free to comment further...
Kindly,
Alan
PS I will be off work for the next week, so nothing will happen till late November or mid-December 2023.