Well done for looking.
Out of interest I have just had a look and I guess to be exact, it depends on what typeface you use but from a quick test I think it's safe to say that either 12 or 13pt for font_small would be fine.
Here's what I found with three different typefaces:
Lucida Grande: font_small=13pt, font_console=10pt
Tahoma: font_small=13pt, font_console=11pt
Arial: font_small=13pt, font_console=11pt