I have a child theme based on Imbalance 2 and I'm trying to create a function in my functions.php to override the 'homepage-thumb' set in Imbalance 2's function file. But I can't figure out a way to do this without changing the Imbalance 2 function file (which I don't want to do). Does anybody know how to do this? Or is there a better solution to my problem: I want to have the thumbs be 220px instead of the theme's 210px. What is the best way to do this?