I'd appreciate to have the same font size as build-in because that size looks best and is most readable.
to reproduce, take a screen-shot, close FC, rename lng-folder, start FC. now compare the build-in caption font size with the size when english.lng was active.

I know there is an option "Use small font" in "Define favorite toolbars" dialog, but when selected
the font is smaller than the build-in font size.