I used the top meters for the fine tuning and level setting. I then have the box in my gear bag with the side meters facing up so I can keep an eye on them. Not sure put they look more like a peak hold type and they were prettly accurate but slow.
If you're using it with the stock firmware, the side meters will act as peak hold's...just so you can make sure you aren't clipping...
but if you upgrade the firmware, they've included the ability to make the side meters either peak hold or full, constant metering.
When it first came out I bought one and bugged Fostex to make it so, and they finally did.