Help Controlling specific particle force / custom constraints.

[PossPoss]

I've narrowed down the steps to reproduce into
1. Start a fresh project with just OBI
1. Go to the softbody example dragon scene, copy the dragon and skin 
2. Go to the rope example snake scene, past the dragon and skin under the obi solver
3. Ensure the dragon is inside the environment bounds and the particle picker has the solver set
4. Play the game and move the worm into the dragon 
5. Crash 

The error it gives is 

IndexOutOfRangeException: Index was outside the bounds of the array.
SnakeController.AnalyzeContacts (System.Object sender, Obi.ObiSolver+ObiCollisionEventArgs e) (at Assets/Obi/Samples/RopeAndRod/SampleResources/Scripts/SnakeController.cs:61)
Obi.ObiSolver.EndStep (System.Single substepTime) (at Assets/Obi/Scripts/Common/Solver/ObiSolver.cs:1598)
Obi.ObiUpdater.EndStep (System.Single substepDeltaTime) (at Assets/Obi/Scripts/Common/Updaters/ObiUpdater.cs:92)
Obi.ObiFixedUpdater.FixedUpdate () (at Assets/Obi/Scripts/Common/Updaters/ObiFixedUpdater.cs:52)

Line 61 is where you set the traction within Analyze Contacts, so my running theory is snake feet don't like touching dragon skin.