Sorry I never got back to you. I just gave up on this for a while. I've been provided with a virtualbox linux image with SOFA framework and the soft robotics plugin already installed, by the people who develop the plugin.
I have yet to try it but I attended the SOMA 2017 summer school and the people from Oliver Brock's lab showed a lot of videos of it working really well. I intend to try it in the next couple of weeks.
Will let you know how it goes.
For posts about your own soft robot designs. Look here for Super-Releaser official releases, robot downloads, and details on specific designs.