I am attaching a data file that has it so that Size is listed as a derived attribute. A Small-Folk would show up as a -1. It also adjusts the Toughness for you, and it has two stacking skill modifiers (which show up like Charisma modifiers for Persuasion, and are therefore not actually printed out). One is a modifier to Stealth skill, where a negative Size grants a bonus, and the other is Intimidation, where a positive Size acts as a bonus.