As requested, we have tested Render 8 using iGrafx FlowCharter 2015 and found that it works without any changes to the Render software. The Render 8 Installation Guide has been updated to reflect this fact.
If you have already installed iGrafx FlowCharter 2013 on your Render VM, you can easily upgrade to iGrafx FlowCharter 2015 using the section titled "Periodic Maintenance of the Render VM" in the Render 8 Installation Guide. When you get to the step about running Windows Update, etc., uninstall iGrafx FlowCharter 2013, install/activate iGrafx FlowCharter 2015 per the instructions, and then complete the remaining steps in the Periodic Maintenance section.