[qualiteam]

\XLite\View\Model\Product is not used anymore since the 5.3.0 version.

You should look into decorating the following two classes:
- \XLite\View\FormModel\Product\Info - defines form fields (for examples search in the soruce code for defineFields() method and how it uses static::compose() to combine existing and custom fields into groups)
- \XLite\Model\DTO\Product\Info - translates model properties/methods to form fields and back (look into init() and populateTo() methods and how these use static::compose() and static::deCompose() methods when fields are to be grouped into lines).

You don't need compose() and deCompose() methods if your custom fields appear as new lines (you use these methods only when your custom fields should appear along with other field in a single line, next to each other).