I was wondering what I would need to be able to put the 28s on the Sportsman? Anyone have any on theirs? If so how well do they perform?

You'll need a lift kit for sure, and I would stick with 26"ers. I have 27" on my SP non HO, and next will be 26", but aggressive like the Outlaws.

Well I am running 28x12.5x12 Outlaws all the way around my bike , and was running 28x10.5x12 all the way and love the Outlaws. You will need a lift kit for sure, and some power mods will help. The 28" will probably cause you some grief as far as possible breaking of cv joints, but I have only broken one and I was running 27x12x12 Vamps at the time.
It is all what you ride the bike for and how hard you ride it that will determine how you hold up to the 28" Outlaws, but cant beat them in the mud!

Thanks,For the replies.Im thinking I will probably go with 26s.