I just installed the Nomadic Tail Rack on my 2017 500 RR-S. It's a nicely built rack that fits well.
http://www.nomadic-racks.com/index.php?option=com_rokecwid&Itemid=62#!/2010-2017-BETA-RS-RR-S-DUAL-SPORT-RACK-KIT/p/12000059/category=21227040
The installation is pretty straight forward. You do have to loosen the muffler and pull it away some for clearance but you do not have to fully remove it as suggested by the instructions. Take care with the threaded inserts in the plastic subframe, they seem easy to cross thread. I didn't but one of them felt like it wanted to and I was extra careful to make sure it didn't.
The plastic subframe appears to be the weak link in the system. When you press down on the rack with some force you can notice the subframe flexing before the rack does. Nomadic states a 20 lb load capacity and I might feel more comfortable with 15 lbs in rougher terrain. I have not tested it fully yet so no comments on durability. My Wolfman Peak Tailbag fits on the rack quite nicely.
Here's a few shots of it installed.