There's no way to do that. Changing the system's small icon size will probably make a bunch of programs look odd, too.
I would write to GPSoftware voicing your support for a Details-with-thumbnails/large-icons mode.
In the mean time, Tiles mode is the closest thing. That lets you see whichever file details you want (editable per file-type) alongside large icons and/or thumbnails for each file. You could make some toolbar buttons to set the sort mode if you find yourself missing the sort headers from Details mode.
Of course, Tiles mode is still quite different to Details mode in the way the information is organised.
So long as the submission was successful it should reach GPSoftware. I didn't think the GPSoftware website would accept submissions without either a registration number or the email address used to get an evaluation but if it did let you then there's no need to re-submit.