Can you reinstall a Doughboy expandable liner by taking the coping off?

No! Leave the coping on the pool. Pull the liner over the top of the coping and clip it where the liner is sagging down and only touching in the middle without any wrinkles and then start the water. As the pool fills readjust the liner. Click this link to download the full instructions from Doughboy http://www.doughboy-pools.com/img/documentsearch/pdf/AG02DOUGHBOYRND.pdf