Having vision and imagination go with quilting 101. I don't think the person at Home Depot has the vision or imagination to help you do this project. As long as the extension is supported well you should be able to add to the desk. You might want to be sure that you can drop the extension when not in use. The piano hinges are a good choice for the weight. Make sure your legs are foldable so that you can put things away nicely. It is doable as long has you have the vision.