The intent of the long message footer is to provide basic subscription preferences (and group unsub functionality) to those who might never visit your group via the web.
If you have a custom message footer for your group, remove it. But it sounds like you've already done that.
In Message Policies, you can set a reply option and then click the box to "remove other reply options." This will make the footer somewhat shorter (at the cost of taking away some of your subscriber's reply options, of course).
Other than that, I'm afraid there's not a whole lot that you can do.?
Hope this helps,
Bruce