You asked this question in November, The first reply was useless and it comes 3 months later... From what I could find the only way to change your seed and world size is to edit your bat file, I'm not entire sure because no one really posts instructions for this anywhere. From what I can tell you are forbidden from editing this file on Survival servers. You have to submit a ticket and then wait for someone else to do it for you...
Of course this is what they are looking for, good grief are you dense. How about answering the question instead of answering a question with a question.