Is this "event" review?
Or external editing?
If you are trying to review recorded footage from several cameras at once simultaneously as things unfolded; ivms should be able to handle that at 4-6 up or so. Using event search, select all cameras, pick day & time range, hit synchronous playback button. I was playing around with it the other day, discovering I needed to sync all the cameras' time settings ... seeing a car go past the house before it'd entered the driveway kind of thing with three cameras.
Manually across an external player would be pain trying to line those up, due to the nature of stop & go motion recording, hitting in a certain sequence as a person or vehicle goes in and out of view of different cameras.