Rigs MUST be rated below their actual average hashing speed. Your declared speed must be at least 1Kh/s below the 24 hour average hashing speed of the rig.
Miavator -- Why is this a requirement to lease a new rig?
If I want to rate my rig above or below actual, what difference does that make to you? You're already flagging rigs that are hashing "below" actual, so renters can see that and make their own decision on whether to that rig rent or not.
If you want to make sure that rigs are accurately rated on the site for some reason, I think the best approach would be to pull the rig owner rating off the site entirely. Just show actual hash speed and be done with it.
I think you may be alone in that.