I went up to a friendly gym and quickly discovered my 1502 cp vaperion could take on the1719 cp flareon twice per full potioning. I the gym one level, left a defender and proceeded to raise the gym 2 more levels. I was about to leave when I discovered someone had just left another 1750 cp flareon. My 1502 vaperion could take on both flareons at 1154 prestige points a pop! I raised the gym another level. In total I raised The gym 4 levels. It was level 8 when I finished. There was one unfilled slot. Based on how quickly the other slots got filled, I'd be surprised if it was open very long after I left.