You can upgrade from a DL coded U fare on VS metal to a VS coded P seat on VS (not a DL coded P fare) with a GUC. P is the VS award class used for their PE cabin. So you need to search for award availability on VS flights, not revenue fare availability. I wouldn't hold out much hope for VS releasing any P availability to DL within next week. I had to search a few weeks out to find any flights with availability. If you purchase a DL coded P/A/G fare on VS metal, you can upgrade to a VS coded G seat with a GUC which is their award class for Upper Class seats. But again, VS tends to limit how many seats they release in G class to DL for awards.