Hi,
the per particle eccentricity channel seems to be broken. I appended the channel correctly with its special name “Eccentricity” and filled the per particle values in my stream accordingly; just as I do for per particle emission, density etc…which all work fine but eccentricity does not.
I assume you are setting the renderer to use your custom channel, but can you double check that you are calling:
shader_schlick s; //if you're using Schlick
s.use_phase_eccentricity_channel( true ); //Is this being set to true?or
shader_henyey_greenstein s; //If you're using Henyey-Greenstein
s.use_phase_eccentricity_channel( true ); //Is this being set to true?I will also dig into the code and see what I can find.
Conrad,
Excellent! no you are absolutely right! I forgot to set this with the new changes of mine. 
Very glad it is my fault and thanks for the quick response!