^17 pound.
And while I personally think the only difference it would have made would be making GSP's ground and pound less effective and riding out to a UD, we can't say it wouldn't have made a difference. The fact is GSP's corner greased his back, making it nearly impossible for Penn to use his BJJ, which is arguably his biggest strength. We can't sit here and say it wouldn't have made a difference, no one knows "what if". It was blatant cheating and in my opinion should be ruled a no contest for that reason.
Of course that would suck because it would fuck everything up in the LW and WW divisions just for Penn to get his ass kicked again, but you can't have fighters flat out cheat like that in front of everyone with no consequences.