Help! adding default size options to live component

Hello, I am creating a live component for an acoustical panel. Right now it has the ability for custom length and width adjustment, and thickness.

I want to be able to have a list of predefined sizing options. For example, for height, I want a dropdown list to choose between 4 feet, 6 feet, or custom size. For width, I want a dropdown list to choose from 4 feet or custom size.

There was a post similar to this that I viewed ( Choosing a size from a predefined list of options ), but couldn’t transfer it over, because it wasn’t using an already made sketchup model like mine.

Any help would be greatly appreciated. Here is the link to the component, thanks.