Good question, it should be possible, there’s nothing against having a font-size defined above 100%.
However %age for font-size is not needed unless you use it in combination with em in a certain way, for a certain goal. % for font sie refers to the computed font-size of the parent element.
There’s most likely a better unit for you to use for your font-size: CSS Font-Size: em vs. px vs. pt vs. percent / Kyle Schaeffer