I didn’t make measurements, but those scans look very flat - nice!
If you upload a similar low resolution scan of the other side (just the scan without any profile), if it would help I would try to make an ICC profile for the scanner using ArgyllCMS, just to see if results look believable without any surprises in the procedure. I’ve never profiled a scanner, but it can’t be that different from profiling a camera.
If you’d rather experiment first before sharing (totally understandable!), here’s the relevant ArgyllCMS “how to” page:
http://argyllcms.com/doc/Scenarios.html#PS1
And here’s where to download ArgyllCMS if you don’t already have it installed (or don’t have the latest version): http://argyllcms.com/ - just scroll down to where it says “Downloads” - there are separate downloads for various operating systems.