On Deb's website, it says that you can get a 2 day, but maybe it is wrong. If we can't get a 2 day UPH, then I wouldn't want it. Two days at the parks is enough for us.
I believe the min for non DVC is 3 days but for DVC it's 2 days but must be for the length of stay. You can frequently drop the first and/or last day as long as it's at least 2 days left.