Here are the screenshots for this book from the Mobileread library:
https://www.mobileread.com/forums/showthread.php?t=44226
I didn't use Calibre, I just copied the epub to the device, first with an .epub file extension, next with a .kepub.epub extension.
Both are open with exactly the same font settings: family=Georgia, size=31, lineHeight=0.88, margin=3
(Note that my Glo is running firmware 3.2.0 and is patched. The patch means that even though the font sliders are all at about the midpoint, the values they give at that midpoint will be different to an unpatched Glo. However the values are exactly the same for both books, so this shouldn't affect the relative size difference between books.)