I have tried this plugin on two different WordPress Setups/MultiSite Networks and have had the same successes (love the plugin) but also the same issue. It doesn’t copy over the featured image from the source article to the destination posts. I tried this over a course of about 7 months, testing various things to no avail. If you would like to try it out on our network, we are testing this on a staging network right now, so no worries about messing things up …. I will gladly give you access.
Thanks for your help in looking at this, I look forward to hearing from you!