Five cats = Littermaid Mega.  I actually have two Megas because there is always an after breakfast and after dinner rush to use the Littermaid and the unit does have difficulty scooping two large litter clumps at the same time, it can be too heavy and sometimes will take several attempts to succesfully scoop the two large litter clumps.  Also, when you have two cats jockeying to use the Littermaid at the same time, well I just had to get another to keep everyone happy!  As other users state, do not overfill the pan.  Also, line the plastic litter hoppers with grocery store bags and you can reuse, reuse, reuse, reuse them many, many times.  When the plastic litter hoppers crack, I reinforce them with clear packing tape and further extend the use of each one.  My cats all love their Littermaid Megas and we couldn't do without them.  With five cats, I usually find myself emptying the hoppers every other day and doing periodic maintenance on the litterpan to keep it free of flat clumps that stick to the bottom of the pan.  Great invention, wouldn't do without it!!