Ring subjected to four forces.

Skunks technique is valuable for cases of static equilibrium with "no constraints".  The constraints are only used to prevent rigid body motion.  Most common is to use inertia relief to prevent rigid body motion.  

In this posting I uploaded an old 2005 PTC technique that I could no longer find in the knowledge base.  Also there is a link to its usage for a thermal case.

https://community.ptc.com/t5/Simulation/Simulation-of-a-lifting-CE/m-p/545154/highlight/true#M220

Oh, also the choices/planes where constrained determines the =ZERO displacement locations.  If I remember correctly inertia relief chooses a zero displacement locations in some way based on the WCS. For displacements regarding these techniques be careful about the zero reference.