Technically the Obsession is not legal for any class of pattern. It is too big and too heavy. That being said, I don't know of any Contest Director that would not let you fly it in Sportsman class and maybe higher. Ideally, the CD would list in the contest sanction that they will allow non-conforming planes in Sportsman class. Since a competitor "could" challenge (protest) the plane and make the CD disquality the plane if the deviation from the 2-meter and 11lb limits are not advertised prior to the event. If you want to fly in a contest, just call the CD ahead of time and ask if it will be ok. The contest that I am running specifically lists in the sanction that ANY AMA legal plane will be allowed in Sportsman. So, go and have fun although there are better choices than the Obsession. Remember that lighter flies better and that the 12lbs + on the Obsession will be a liability.