We have purchased the Abundance theme and have created a custom css folder for all of our css changes, which I understand won't be affected with any future updates. My question, however, relates to some custom PHP. For example we changed the percentage of the image container on the product page as well as the percentage of the product description container. We have our product page looking how we would like, but are pretty sure that future updates would overwrite our PHP changes. How can we make these minor alterations without being affected with future updates? Please advise.