Hi Mike,
Looking at the java code, it appears the the memberstoskip should be a comma separated list. I also see in the code that it automatically adds the createdDate and changedDate objects:
List<String> toskip = Arrays.asList((membersToSkip + ",createdDate,changedDate").split(","));
So in a perfect world, you should not need to specify that createdDate and changedDate should not be changed. I suspect that changedBy should be added to your memberstoskip list as 'yourlist + ',changedby'
Let me know if that works for you,
Rob