I was thinking of this when you mentioned the ropejack before. With two people on the ground it would be especially easy, but it's doable with one. Put a prusik on the downline of the rigging rope. Attach a pulley to it that has some kind of lower becket. Anchor a short second line to the becket, run it through another pulley that's anchored to the top hoop on the porty, then up and through the prusiked pulley on the line. One person can haul on that to remove slack, while the second wraps the porty to maintain progress. Once it's tensioned, the stuff can be removed from the rope. Cost is either ~$75 to buy everything new, or free if you already have the stuff. I already have the stuff.