is the rigging toolkit compatible with maya 2016?
Last I tried doing a mirrored rig I ended up getting very strange artifacts - has this been updated and should work as well?
It may work with 2016, but there are bound to be issues, even some that have been reported on here and the forums.
Officially it has only been tested on Maya 2012 - 2014.
You can always check this thread for any information: Animation and Rigging Tools: FAQ, Known Issues and Feature Roadmap - Character & Animation - Unreal Engine Forums