Multiple scattering with Arnold

[mattv]

Has anyone else had difficulty getting Multiple Scattering to work with Arnold renderer? I've tried some really high values but am unable to get it working in my renders. I did not see any specific Arnold render settings in the render settings window other than increasing the volume indirect AA samples and the volume ray depth. I've tried various values there as well with no success.

This is an example side-by-side of MentalRay (in Maya 2015) vs Arnold (in Maya 2017) with the same settings. Any assistance would be much appreciated.