I rented an 80l bladder press and fit all the skins into one pressing. Free run filled the 15 gal. keg and I pressed another 5 gal. I broke up the cake a little and re-pressed, gaining two more gallons. The flavors of the pressed juice are a little more tannic and slightly more acidic.
Including the 3 gallons of juice I pulled off early, Iended up with about 25 gallons total.
The bladder press was great, very easy to use and gentle on the grapes.