X-Men - The Arcade Game [NPUB30320]

Anyone tried this game with six controllers? With six xbox one wireless controllers and set to mmjoystick (xinput only supports 4 controllers), I have a 6-player game. With up to 5 controllers, the game runs fine at about 60fps. But once I start the game with the 6th controller, the game stutters along at sub-20fps. Weird.

FYI: played Bomberman Ultra with 7 wireless controllers and performance was fine.