Spine could be flatter but in this case no matter.
Excelent quality.
Just for kicks, could you take 3 test scans.
One where other settings are same as your scan but DPI is changed to 300.
One where other settings are same as your scan but Unsharp mask is on.
One where other settings are same as your scan but Image adjustment is on.
Just wanting to see if quality could be tweaked just bit better.
But if you can't bother, I understand.