you dont need 4 of them. one is enough.
Is the disk away enough from touching the floor?
Once i made a Cage-style bot, with chassis on very top, a SLOW linear actuator(normal, heckalot weight attached) and wheels on bottom. hover engine was too away from a surface to lift something. and cage was too high for other bots to harm it. a servo motor was atached to a wedge and a wall in a 90 degree angle, and once robot was in, the servo would be activated, and turn the wedge into wall and wall into the cage floor. then the linear actuator would be set up activating the hover lift sensor. making bot to fly up to ceiling, slowly or very fast according to actuator position and lifting the other bot too. then the servo would turn another 90ยบ angle once robot is on ceiling, turning wall into floor and floor into... something facing down ROTFLMFAO. another version used a faster burst motor to do the drop job.
EDIT FOR IIs REPLY: hes NOT using any antiballast, and dual perms may be too heavy