I tried both Gluon and full Plastic. I'll attach the preview generating script here. It is a slight modification of a previewing script that ships with Blender but with an added output option so we send it to where plastic expects to find the file. Below are the preview settings.
"<path to blender install>\blender.exe"
-b "@src" --python "<path to python script>\bl_previews_render_plastic.py" -- "@output"
bl_previews_render_plastic.py
Also I found this in the logs
DEBUG PreviewRequest - Exception thrown when loading the following preview: <myfile>.blend -> Parameter is not valid.
at System.Drawing.Bitmap..ctor(String filename)
at aii.a(String A_0)
at jl.d(String A_0, Boolean A_1, ach A_2, abz A_3)
at abu.a(Object A_0)