Welcome to the world of fiberglass!
Here are the ratings from:
Subaru Warranty, and Towing information page
2011, 2010, 2009, 2008, 2007, 2006, 2005: 2400lbs with trailer brakes, w/o brakes 1000lbs, Hard towing 1000lbs
2004, 2003 automatic trans 2000#, manual trans 2400#
2002, 2001, 2000, 1999, 1998 2000#
However, when you take data off the internet, it becomes a game of "Who Do You Trust?" (I often wonder why the ratings change year to year.)
The best source for YOUR vehicle is in the owner's manual for that vehicle, (or sometimes the info is on the driver's door and/or pillar).
We purchased a Trillium
1300 because, among other things, it came in under the tow weight
limit of our 2000 Subaru Outback (2000#). (With our 'stuff' in it, we were weighed at Quartzsite as 1840#.)
We, too, use a Porta Potti to avoid night time trips, are happy with the combo, and spent Dec 28 to Feb 19 in our rig earlier this year. I can heartily reccommend that lighter is better. I can push/pull our rig by myself, especially on pavement. That really gets the attention of persons with large, heavy stick builts!