I do know of one person who plays on UB who has a very very good track record playing heads up. I would be sure it's over 65%. He does play the lower amounts as playing $100 HU is not always available. At least, that's what he told me. I did alright myself playing HU and that was before I knew what I was doing. I haven't played HU SNGs lately, but I'm sure I would do just fine.